The book artist, children's writer, and poet Henno Käo was born on January 10, 1942, in Laheküla, Saaremaa. He studied at the Tartu Art School from 1958 to 1963, graduating as a decorator. From 1968 to 1969, he studied graphics at the Estonian State Art Institute, and from 1975 to 1978, he attended Villu Toots' calligraphy school. Käo worked as a puppet film artist at Tallinnfilm from 1963 to 1968 and at the Tallinn Recreation Parks Directorate from 1969 to 1982. After that, he worked as a freelance artist.