Cover photograph: Multispecies microbial communities in situ within 8-h-old dental plaque. Red cells are stained with an antibody reactive with a streptococcal receptor polysaccharide involved in cell-cell recognition (coaggregation). Green cells are stained with an antibody reactive with many streptococcal strains known to coaggregate with the receptor-polysaccharide-bearing cells. Blue cells are stained with a general nucleic acid stain. Mixed-species communities, rather than clonal growth, characterize initial colonization of human enamel. (See related article on page 3400.)