Cover photograph (Copyright © 2006, American Society for Microbiology. All Rights Reserved.): Space perspective on a milky sea (blue comma-shaped feature), thought to be caused by enormous populations of luminous bacteria in the northwest Indian Ocean on 25 January 1995. The glowing waters, which spanned an area roughly the size of Connecticut and persisted for at least 72 h, were reported by a merchant vessel and later corroborated by an environmental satellite designed to sense low-light signals. The findings raise optimism for practical study of these elusive phenomena. (Global composite formed by NASA Blue Marble, NOAA/NGDC Nighttime Lights, DMSP/OLS, and MeteoSat-5. Courtesy of S. D. Miller and S. H. D. Haddock.) (See related article on page 2295.)