Recent advances in studies of yeast, Drosophila and humans have renewed interest in heterochromatin. These recent studies have demonstrated the interspersion and rapid spread of transposable elements into Drosophila heterochromatin; documented the requirement of heterochromatic genes for heterochromatin; identified heterochromatin-like regions in yeast chromosomes; confirmed an important role for satellite DNA in human centromere function; and suggested potential functions for heterochromatin-associated proteins.