Laurencin and Picabia were fellow-students in Paris, as Dufy had been in Le Havre (he — and Matisse — became a particularly close friend during Braque’s Fauvist period). Apollinaire introduced Braque to Picasso, his comrade-to-be in the invention and development of Cubism; they saw each other daily for a year and worked closely for five — in Braque’s phrase, roped together like mountaineers. Gris became a very close friend following WWI. Diaghilev commissioned ballet-costumes and sets from him, and Heidegger visited him in the 1950’s. He taught Picasso to grind colours, and once bought him 100 hats at an auction.