After spending his childhood in Patras, he studied at the Athens School of Fine Arts (1886-1893) under professors Nikephoros Lytras and Konstantinos Volanakis. He began to exhibit in 1899 when he participated in the Exhibition of Athens followed by presentations of his works in group exhibitions in Athens (City Hall 1902, Zappeion Hall 1907, 1909, 1910, League of Editors, 1912) and Alexandria (1903, 1906). During the Balkan Wars of 1912-1913, he embarked, by government order, on warships and captured scenes of the actions carried out by the Greek fleet. In a solo show organized by the Artistic Society at the Zappeion Hall, which opened shortly after the artist’s death, more than two hundred and sixty works were included.

Known mainly as a painter of seascapes, he was also involved with landscapes and the depiction of scenes from the lives of farmers and fishermen, sometimes appearing to be an adherent of academicism and others of plein air approaches.

He studied at the Athens School of Fine Arts (1894-1896) under Nikephoros Lytras and continued his studies in Paris under Benjamin Constant, Jean Paul Laurens and Jules Lefebvre. In 1900 he won an award at the International Exhibition of Paris. He settled in Greece in 1903 and in 1911 was appointed professor of sketching at the School of Fine Arts but resigned a few months later. In 1915 he was appointed anew and taught until 1949, while in 1946 he became the director of the School. In 1949 he was made a member of the Athens Academy and withdrew from the artistic scene because of an eye disease which did not permit him to exercise his art any longer.

Mathiopoulos painted symbolic, idealistic and historical subjects as well as scenes from everyday urban life, but he became particularly well-known and popular through his portraits. He primarily made use of pastels and, to a lesser degree, oil and having mastered impressionistic types, rendered his works with elegance and a tendency to idealize in agreement with the aesthetics of the Belle Epoque.

Graduate of the Megali tou Genous Scholi (Great School of the Hellenes) he studied architecture at the Polytechnic School of Constantinople. From 1901 to 1908 he lived in Paris, where he took painting lessons from the neo-impressionist Henri Martin and studied at the School of the Decorative Arts. At the same time his exhibition activity commenced. He returned to his homeland and travelled to the Middle East, painting intensively (1908-1910). In 1913 he moved with his family to Thessaloniki and the following year was appointed chief engineer to the municipality, a post he remained at till 1917, when he settled in Athens. During the Thessaloniki fire of 1917 many of his works were destroyed. In 1918 he became the Director of the Museum of Folk Handicrafts and was appointed a member of the Artistic Council of the National Gallery. In 1920 he travelled to Sparta, Mystras, Olympia and Naxos, and the next year to Thermo, Aitolia, accompanying the archaeologist Konstantinos Romaios. During the period of 1921-1923 he lived and worked in Chios and Lesbos and in 1923 received the Prize in Letters and Arts. A founding member of the Art Group, he participated in its exhibitions, while presenting his works in other group shows and a total of thirteen solo exhibitions. A year before his death at forty-nine years of age, he visited Paris and Munich. In 1936 his works were sent to the Venice Biennale. Retrospective presentations of his work were held in 1929 at the Zappeion Hall and in 1980 at the National Gallery. In addition to his artistic creation he was also active in educational reform and worked in cooperation with Dimitrios Glinos, Alexandros Delmouzos and Manolis Triantafyllidis.
A revitalizing influence in Greek painting, using impressionist and post-impressionist models as his starting point, he produced mainly landscapes, in which schematization and powerful, pure colors dominate and in that way build a composition made up of unities.

On a scholarship from the Ioannis Capodistrias government he studied painting in Rome. He returned to Greece in 1837 and five years later was appointed professor at the School of Arts where he taught until he was discharged in 1862. After one trip abroad, he worked in the photographic studio he kept in Athens. Together with his brother Georgios, he took part in the decoration of the palace of Othon, while he also worked on the organization of the Greek pavilion at the World Exhibition of Paris in 1855, where as an exhibitor he presented photographs of the monuments of the Acropolis. The same year he exhibited his photographs at the National Technical University in the framework of its yearly exhibition, while in 1856 he was a member of the critical committee of the Kontostavleios Competition and presented photographs of the Parthenon reliefs and portraits at the exhibition at the National Technical University. As a photographer again he took part in the International Exhibition of London in 1862 as well as the II Olympia Exhibition in 1870 where he won the silver medal, second class. In 1870 he also made photographic portraits of King George I and Queen Olga.

In painting he was principally involved with portraiture while he also depicted subjects from the Greek War of Independence in paintings which bear witness to his Italian training.

He studied painting at the Athens School of Fine Arts under Konstantinos Parthenis (1945-1951). On a scholarship he continued his studies at the School of Decorative Arts in Paris (1961-1963). He has also been involved with set design, costume design and book illustration. He has had solo exhibitions and taken part in group shows.

In his painting he combines a lyrical mood with a realistic style to depict everyday scenes, still lifes, landscapes and human figures.

He graduated from the Greek-French Lycee in Alexandria where his family had emigrated. In 1915 he enrolled in the third year of the Athens School of Fine Arts and attended classes until 1917, taught by Dimitrios Geraniotis and Georgios Jakovides. He travelled to Europe and then stayed in Paris till 1926. There he associated with artists such as Picasso and Derain and probably studied at private academies. He returned to Greece, earned his degree from the School of Fine Arts and at the same time got a three-year scholarship from the Voltos Bequest for Paris where he stayed until 1930. He studied philosophy and psychology at the Sorbonne and wall painting and interior architecture at the School of Fine Arts. In Paris, where he had his own studio, he got to know the gallery owner Manolis Segredakis, who became the prime supporter of his work. In 1931, having already settled in Greece, he held his first solo exhibition, on which the critics were divided. In response to a negative article by Zacharias Papantoniou, seventeen intellectuals and critics voiced their support for the exhibition. The 18 κριτικά άρθρα γύρω από μία έκθεση (18 Critical Articles on An Exhibition) signed by, among others, Fotos Politis, Spyros Melas, Dimitris Pikionis, Stratis Doukas, and Christos Karouzos, is considered to be the manifesto of modernism in Greece. In 1932 he worked with Pikionis on the sets for the performances of the Kentrikon Theater in Athens and starting in May 1935 worked with Fotis Kontoglou on the restorations at Mystras. In 1935 he settled in the United States and had a solo show in New York. Starting in 1937 he worked with large American film-making companies in the design of publications and posters. At the same time he travelled on the American continent under the name George de Steris. In 1939 four large wall paintings by him with the history of Greece as their subject ornamented the Greek pavilion at the New York World’s Fair. In 1949 he became an American citizen under the name Guelfo Ammon d’Este. Between 1950 and 1965 he gave painting lessons and did the paintings for the cathedral church of New York and the church of the Holy Trinty in Lowen, Massachusetts. From 1965 to 1975 he taught at the Traphagen School. From 1980 to 1985 he settled with his wife Anna Vassalo Savino in Nice, France. In 1985 he returned to New York. In 1988 his wife brought his ashes back to his birthplace.
Although Greece had lost track of him since the beginning of the Fifties, he had held shows there (Nees Morfes 1969, Macedonian Art Society “”Art”” 1970, Trito Mati 1978). Presentations of his work were also organized at the Sculpture Gallery of Munich (1980) and the National Gallery of Athens (1982). In 1991 the Municipal Gallery of Thessaloniki organized a retrospective in his honor which was also taken to Athens, and shown at the Melas Mansion (1992).
He is considered the forerunner of Greek modernism. The thematic and plastic freedom of his painting, the symbolic extensions and references to metaphysical art, created a split in the visual reality in Greece in the period between the wars. From the abstract form of his first creations he was led to a realistic style with a decorative aspect to it, in the works he painted in America.

He studied at the Athens School of Fine Arts (1864-1871) and after a brief stay in Munich, where he enrolled at the Academy, and in Paris, he finally settled in Brussels in 1872. There he became friends with the painter Guillaume Vogels and joined up with the avant garde movements of the time. He took part in many exhibitions in Belgium (Ghent, Brussels, Antwerp, Namur, Charleroi) while in 1878, at the International Exhibition of Paris, he participated in the Greek division. The same year the Artistic and Literary Circle of Brussels organized his solo show. In 1880 he travelled to southern France and Greece, where he took part in the exhibition at the Melas House in Athens (1881). He returned to Brussels at the beginning of 1881 and a little later the first symptoms of tuberculosis appeared, an illness that was to take his life. In Belgium he was a founding member of the Circle of Chrysalis (1875) and participated in its exhibitions (1876-1878, 1881), the Circle of Water Colorists and Engravers (1883) and the Circle of XX , at the first exhibition of which, at the beginning of 1884, a few days after the painter’s death, his works were included. Retrospective exhibitions of his work have been presented at the Town Hall of Saint-Gilles in Brussels (1993), Namur (1994), the Gallery E. Averoff in Metsovo and the National Gallery (1996).
His creative work includes scenes from daily life, still lifes, portraits and landscapes. Developing innovative themes he showed through his multifaceted work, which reflected the artistic quests of the period in a condensed form, that he was one of the leading figures of modernism at the end of the 19th century.

He studied painting at the Athens School of Arts (1850-1856) taught by the brothers Philippos and Georgios Margaritis, the monk Agathangelos Triantafyllou, Raffaello Ceccoli and Ludwig Thiersch, whom he also assisted in the iconography of the Russian Church in Athens (1853-1855). In 1860 after teaching Elementary Graphics at the School of Arts for two years (1856-1858), he left for Munich where first on a scholarship from the Greek government and then with the support of Baron Simon Sinas, he completed his studies at the Academy of Fine Arts, his principal teacher being Karl von Piloty. In 1865 he returned to Athens and the following year was appointed professor of painting at the National Technical University, remaining in that position till his death. He was a close friend of Nikolaos Gyzis, with whom he visited Asia Minor in 1873, Munich in 1874, where he stayed until 1875, and Paris in 1876 while in 1879 he also travelled to Egypt.

In 1855, while still a student, he took part in the International Exhibition of Paris, in which he also participated in 1867, 1878, 1889 and 1900, winning the bronze medal at the last two while in 1873 he took part in the International Exhibition of Vienna. At the same time he was extremely active in Greece, participating in 1881 at the Melas House Exhibition, in 1888 at the Panhellenio in the Zappeion Hall, in 1896 at the Panhellenio organized in the framework of the Olympic Games, at the exhibition at the Parnassos Hall and so on. After his death, his works were presented at various exhibitions in Greece and abroad, such as the exhibition “The Piloty School 1858-1886” held in 1909 at the Heinemann gallery in Munich and the International Exhibition of Rome in 1911. Moreover, in 1933 the Athens School of Fine Arts organized a large retrospective exhibition of his work.

Nikephoros Lytras was one of the leading representatives of the School of Munich and is considered to be the father of modern Greek painting. Though he was acquainted with impressionism, he remained faithful to the academic tradition and was involved with nearly all forms of subject matter: portraits, still lifes, historical scenes and mythological motifs. But the most important part of his work consisted of genre scenes, which he, in essence, introduced to Greek painting and which contain scenes from the Greek provinces and the urban area, the Greek family and the world of the child, as well as other subjects from further East. He is also considered to have been an innovator in the sector of portraiture, where his endeavour to penetrate into the psychology of the figure being depicted can be readily seen. His teaching contribution was also of great importance, decisively influencing the following generations through his nearly forty years at the Athens School of Arts during which he undertook large-scale endeavors for the upgrading of the lessons and the reorganization of the artistic division.

Italian in origin, he studied painting at the Venice Academy of Fine Arts where, after his graduation, he worked for a time as an assistant to the Chair of Perspective. After the failure of the Italian revolt against the Austrians in 1848, in which he took part, he took refuge as a political exile first in Patras and two years later, Athens. For his contribution to the struggles for his homeland he was later awarded the silver decoration of the Savior and three Italian medals.

With the backing of Queen Amalia, he decorated her country residence while, at the command of Othon, he completed the iconography of the Russian church, which had been begun by Ludwig Thiersch and Nikephoros Lytras. For his work the Tsar of Russia Alexander II awarded him the Gold Medal. He was also commissioned by Othon for the painting The Army Camp at Thebes which established him as a painter, and he decorated the ceiling of the ceremonial hall of the University of Athens. From 1863 to 1901 he taught Perspective, Stage Design, Elementary Drawing and Decorative Design at the School of Arts and painting at the Evelpidon (Military Cadet) School.

In 1859 he took part in the Olympia Exhibition and participated again in 1870, winning the silver medal. At the same exhibition in 1888 he was awarded the bronze medal. He also took part in the International Exhibition at Paris in 1867 as well as exhibitions at the Parnassos Hall and was a member of many critical committees.
Employing water color for the most part, he depicted archaeological sites and monuments, establishing this as a special kind of landscape painting. In his work academic, classicistic principles coexist with a more realistic approach and colors are rendered with particular sensitivity.

Despite the humble origins of his family, he studied at the Athens School of Fine Arts and was distinguished for his abilities. On a scholarship he continued his studies at the Munich Academy as a pupil of Ludwig von Lofftz and Wilhelm Lindenschmidt. In Munich, where he remained till 1879, he became friends with Nikolaos Gyzis. In Athens he presented his work in many group exhibitions (Melas House 1881, Parnassos Hall 1885, Zappeion Hall 1888, 1896) and received the bronze medal in the competition at the Parnassos Hall in 1890; he also participated in the World Exhibition of Paris in 1900 and the International Exhibition of Athens in 1903. He went into seclusion on the island of his birth and during the final decade of his life took part in only two exhibitions in Athens, in 1908 and 1910, consisting exclusively of old works, and he was gradually forgotten.

Already during his student years he was interested in genre painting, portraiture and the depiction of everyday scenes and objects. He gave the best example of his creative powers in his landscapes, rendering the unique flavour of the Greek landscape in agreement with those plein air tendencies which expressed themselves in Greek art during the final twenty years of the 19th century.

He studied at the School of Arts (1902- 1906) under his father Nikephoros Lytras and Georgios Jakovides. In 1907 he continued his studies at the Munich Academy under Ludwig von Lofftz. In the Bavarian capital he came into contact with German expressionism and the creations of the Blue Rider group. After his return to Athens in 1912 he began to participate in the exhibitions of the League of Greek Artists (1915, 1916, 1917, 1920, 1926) while in 1919 he exhibited in tandem with the sculptor Grigorios Zevgolis. He was a founding member of the Art Group. In 1923 he was elected professor at the School of Fine Arts. After his death, retrospectives of his work were organized in 1929 at the Zappeion Hall and in 1936 at the Venice Biennale.

Nikolaos Lytras, Konstantinos Parthenis and Konstantinos Maleas are considered to have revitalized modern Greek art at the beginning of the 20th century. He influenced the development of Greek painting both through his teaching at the School of Fine Arts and his pioneering art work. Portraits, landscapes and still lifes were built up with broad, free brushstrokes of viscous color and gestural writing.