Light controls various developmental processes in mosses. On pages 373–386 of this issue, Imaizumi et al. report that blue light signals, which are perceived by the photoreceptor cryptochrome, control developments in Physcomitrella patens. There are at least two cryptochrome paralogs (PpCRY1a and PpCRY1b genes) in the moss genome. Using cryptochrome knockout mosses revealed that blue light induced side branches on the moss protonemata via cryptochrome. The protonemata of the recombinant moss (cry1a cry1b-1), in which both cryptochrome genes were disrupted, produced few side branches under blue light. The cover picture shows blue-light grown protonemata of the PpCRY1b cDNA overexpressors in cry1a cry1b-1 background. The overexpression of one of the cryptochrome genes rescued the side-branch-phenotype of the cryptochrome double disruptant. The protonema cell walls were stained with Calcofluor White to help distinguish each cell. Imaizumi et al. showed that cryptochrome light signals control not only side branching but also other developmental changes, such as gametophore growth. Cryptochrome might control these developmental events to partly suppress auxin signals.