Lygia Pimentel Lins (23 October 1920 – 25 April 1988), better known as Lygia Clark, was a Brazilian artist best known for her painting and installation work. She was often associated with the Brazilian Constructivist movements of the mid-20th century and the Tropicalia movement. Along with Brazilian artists Amilcar de Castro, Franz Weissmann, Lygia Pape and poet Ferreira Gullar, Clark co-founded the Neo-Concrete movement. From 1960 on, Clark discovered ways for viewers (who would later be referred to as "participants") to interact with her art works. Clark's work dealt with the relationship between inside and outside, and, ultimately, between self and world.