No. 1
1962
Mark Rothko is very well known for his pieces that deal with rectangles, usually, but not always, as a set of three rectangles placed one above the other (this style is known as Color Field). Two such pieces are shown directly above and below this paragraph.
Earth and Green
1955
Rothko also experimented with various other styles, including different varieties of Abstraction and Expressionism. I've placed a few especially beautiful paintings below.
Untitled
1939
Untitled
1944-1945
Underground Fantasy
1940