In 1963, Guidon organized an exhibition of prehistoric paintings at the Ipiranga Museum. She was approached by a visitor from Serra da Capivara, who showed her photographs of rock art from rock shelters in the area. Guidon recognized that the paintings were significantly different from any known at that time, and was struck by their diversity and abundance. A few years later, Guidon visited the rock shelters at Piauí herself, and began research in the area in 1973. In 1978, she convinced the French government to establish an archeological mission to study prehistory in Piauí. Guidon led a mission composed of national and international researchers and local field assistants until her retirement, at which point Eric Boëda, a researcher at the CNRS and professor at the Université Paris, took over at her invitation.