Morellet then adopted a pictorial language of simple geometric forms: lines, squares and triangles assembled into two-dimensional compositions.

In 1960, he was one of the founders of the Groupe de Recherche d’Art Visuel (GRAV),[3] with fellow artists Francisco Sobrino, Horatio Garcia-Rossi, Hugo DeMarco, Julio Le Parc, Jean-Pierre Yvaral (the son of Victor Vasarely), Joël Stein, Vera Molnár and François Molnár (the last two left the group shortly after).

He gained an international reputation, especially in Germany and France, and he was commissioned to create work for public and private collections in Switzerland, Great Britain, Italy, the Netherlands and the U.S. One of his works is part of the permanent collection of the Centre for International Light Art (CILA) in Unna, Germany.

In 2016/2017, the CILA staged a retrospective of Morellet's Light Art, the last exhibition to be curated by the artist himself, shortly before his death in May 2016.

Kunstmuseum Reutlingen | konkret From 2017 until 2020, Morellet's estate worked with Lévy Gorvy before moving to Hauser & Wirth.