Piet Mondrian (born March 7, 1872, Amersfoort, Netherlands—died February 1, 1944, New York, New York, U.S.) was a painter who was an important leader in the development of modern abstract art and a major exponent of the Dutch abstract art movement known as De Stijl ("The Style"). In his mature paintings, Mondrian used the simplest combinations of straight lines, right angles, primary colours, and black, white, and gray. The resulting works possess an extreme formal purity that embodies the artist’s spiritual belief in a harmonious cosmos.