François Morellet died on Wednesday, just a few days after his 90th birthday. Parisian gallerist Kamel Mennour confirmed the French artist’s passing to Le Monde. Morellet is known primarily as a major figure of geometric abstraction and Concrete Art, working across mediums including painting, sculpture, and light-based art. Though he began working in the 1950s, the artist has explained that he had to wait decades before his neon works became in-demand enough to sell. Morellet was a central player in the founding of the significant Paris collective of the 1960s Groupe de Recherche d’Art Visuel (GRAV).

Some 60 years after his practice began, Morellet received a major retrospective at the Center Pompidou in Paris, cementing his place in the country as one of the key artists of his generation.