Massironi is best known for his minimalist metal furniture designs, which have been featured in numerous exhibitions and collections worldwide. He was also a professor at Milan Polytechnic and published several books on art and the theory of visual perception.
In addition to his design work, Massironi was also a prolific painter, producing abstract works inspired by the principles of geometry and visual perception. He was also active in the field of conceptual art, exploring the ideas of seriality and repetition through his work.
Massironi is considered one of Italy's most influential designers of the 20th century, as well as an important thinker in the fields of art and visual perception.