Studies of endospore formation by Bacillus subtilis and fruiting body development of Myxococcus xanthus have revealed key features of regulatory networks that govern temporal and spatial gene expression in bacteria. In B. subtilis, sigma factor cascades, modulated by other types of transcription factors, regulate genes in two cell types that form and communicate with each other during starvation-induced sporulation. In M. xanthus, starving cells also send signals that alter gene expression, but the cascade to emerge so far involves transcription factors other than sigma factors. A hundred thousand cells coordinate their movements to build a fruiting body in which spores form. The two regulatory networks are compared, and questions that remain are identified.