He has been variously associated with expressionism, cubism and surrealism but his pictures are difficult to classify. They often have a fragile child-like quality to them, and are usually on a small scale. They frequently allude to poetry, music and dreams and sometimes include words or musical notation. The later works are distinguished by spidery hieroglyph-like symbols.

http://www.zpk.org/ww/en/pub/web_root.cfm
http://en.wikipedia.org/wiki/Paul_Klee