Mondrian was the leading artist of the 'De Stijl' (the style) movement, a group of Dutch artists who produced strictly geometric, abstract art. Mondrian's early work painted from nature became increasingly abstract. For example a series of studies of trees and their branches made from 1909 to 1913 evolved into a criss-cross of lines. However it was when he became a member of the Theosophist group that he began to paint the grid paintings with which he is associated. Theosophists saw existence in terms of harmony between male and female, positive and negative, horizontal and vertical. Mondrian's paintings embody this sense of balance.