Fluorescent reporters have become indispensable tools to study both gene expression and the subcellular localization and interaction of proteins in the cell. In this issue, Wildt and Deuschle report the use of the red fluorescent product of the bacterial cobA gene as a transcriptional reporter in bacterial, yeast, and mammalian cells. This new reporter complements the existing set of green and blue fluorescent proteins, and should be less sensitive to the problem of cellular autofluorescence in response to UV light ( see. p. 1175).