Pablo Picasso preferred his mistresses to be submissive and not as tall as him, and “was uncontrollably horny” when he was in his 70s and early 80s, according to John Richardson, who is working on the fourth volume of his biography of the famed Spanish artist.

Richardson wrote “Picasso’s Erotic Code,” for May’s issue of Vanity Fair. Why was Picasso so irresistible to women? Sure, it helps to be one of the world’s greatest artists … but it was all about the eyes, Richardson says.

“Above all, he had what Spaniards call the mirada fuerte, the strong gaze, which, as Picasso said, enables a man to have a girl with his eyes,” he told Vanity Fair. “Picasso had fantastic eyes: enormous eyes that could indicate interest, rage, love, desire, impatience—whatever. I used to watch Picasso working a room. At dinner in the studio, he would get each person—male or female, old or young, friend or acquaintance—with those hypnotic eyes.”

Picasso’s 14-year relationship with his mistress, Marie-Therese Walter, is the subject of a major exhibition at the Gagosian Gallery on West 21st Street, in New York, opening on April 14.