His first personal exhibition, held at the Galleria Il Milione in Milan, where he exhibited many times during his artistic path, was in 1949. After the Resistance, he was leader of the "Pittura" group and editor of magazines such as Il 45 and Realismo, directed by Raffaele De Grada. In the 1950s his works have been selected for the Venice Biennale, as well as for the exhibition of the Realists held at the Leicester Galleries in London and in New York, where he exhibited with a personal show at the Heller Gallery.
During this period the subjects of his paintings were influenced by his encounter with the rural situation in Calabria and by the urban industrial landscape of Milan and Paris, places where he returned repeatedly over the years.
Treccani then developed the various features of his artistic research along parallel lines, continuing to work and exhibit in towns and cities in Italy and abroad, and alternating this “wandering” activity with regular and creative stays in Macugnaga and Forte dei Marmi, places to which the artist was strongly attached in life and painting. In 1978 he founded the Fondazione Corrente,a center for cultural events, exhibitions and debates in the various fields of culture and art, as well as a center for the collection and study of documents related to the period between the birth of the movement and the years of Realism.
In 1989 the City of Milan held a major retrospective exhibition on the artist at the Royal Palace, and another large retrospective of his works was held at Foundation Bandera in Busto Arsizio in 2003. In 2004 he created the cycle of large windows Energia, luci e colori, shown in Lugano, Riga, Budapest and Prague. In 2006 the town of Forte dei Marmi organized the exhibition at the Fortino Le mutazioni del realismo - Opere inedite 2003-06, the result of a renewed search for forms that has its center in color.
In 2008, again at Royal Palace, Treccani participated in the exhibition Corrente, le parole della vita. Opere 1930–1945, with a room set aside for his paintings of that period. A large retrospective exhibition inaugurated the renovated rooms of Palazzo Barberini in Montichiari in May 2009,just a few months before his death, which took place on November 27, 2009, in his beloved House of Swallows.Wikipedia