Cover photograph (Copyright © 2000, American Society for Microbiology. All rights reserved.): Dynamic heterochromatin association of murine Suv39h2 in male germ cells. Double immunofluorescence labeling of Suv39h2 (orange-pink) and Scp3 (green) in a section of testis tissue representing stage VI to VII of the spermatogenic cycle. Suv39h2 is localized at heterochromatin during meiotic prophase (data not shown), at the XY body (orange patch) in mid-late meiotic prophase cells, and at heterochromatin (pink) in haploid round spermatids. Cells in meiotic prophase are identified by immunostaining of synaptonemal complexes (green). (See related article on page 9423.)