A critic, journalist, but fundamentally, a painter and artist who used the medium of plastic, Baj was from Surrealist beginnings, but was a practitioner of Neodadism. Born in Milan on October 13th, 1924, he aimed to present, with a lively interest in social content, the era of nuclear power. In 1951, he started to write for the Italian Nuclear Movement and in the following year, together with Sergio Dangelo, he wrote for the Nuclear Painting Manifesto in Brussels.

During the 1950's he participated in the Movement International pour une Bauhaus Imaginiste. It is at the beginning of the 1950's that he specifically carried out his Nuclear Research and in 1957 he subscribed to the Manifesto against Style with a polemic against all formalistic repetitions in art.

At the beginning of the 1960's he defined the 'pop' image from a European viewpoint and argued that he orientated himself on sociopolitical and moral problems. He lived for a long time in Paris where he got to know Duchamp.

He is author of numerous illustrated books; a selection was published by Electa in 1990, The Books of Baj. His major retrospective 1967, began a long and profitable business relationship with the Milanese Studio Marconi. In the 1980's and 90's he mainly practised as a painter of the grotesque. Among his more important retrospectives, the following distinguish themselves; in 1974 at the Palazzo Reale in Milan, in 1982 at the Palazzo della Ragione in Mantova; in 1990 at the Centre Georges Pompidou in Paris; in 1996 at the Mathildenhohe in Darmstadt and in the year 2000 at the Chartres Museum in France.

He lives and works in Vergiate.