Animals and plants have divergent sets of blue light receptors, called Cryptochromes. However, green alga Chlamydomonas has both animal-like and plant cryptochrome (pCRY). The presence of multiple cryptochrome suggests specific roles in different pathways in respective organisms. In this paper, Müller et al explore the biological functions of pCRY using a mutant with reduced pCRY activity. pcry mutant showed defects in circadian clock with longer period and phase shifts. pcry also show differential expression profile during the life cycle. (Summary by Nidhi Sharma) Plant Physiol.