The cover shows exfoliation of superficial facet cells (green) from the mouse bladder epithelium after infection with uropathogenic Escherichia coli (red), the principal cause of urinary tract infection in humans. Functional genomics studies have revealed molecular mechanisms that operate to replace exfoliated facet cells and that support innate host defense responses triggered by bacterial attachment. For details see the article by Mysorekar et al., pages 7412-7419.7412.