CRY2(PHR) corresponds to the N-terminal photolyase homology region (PHR) of the Arabidopsis thaliana CRY2 gene (TAIR:28374); typically amino acids 1-498 of the protein are used. When exposed to blue light, CRY2(PHR) heterodimerizes with the N-terminal domain of the protein encoded by the Arabidopsis thaliana CIB1 gene (TAIR:130033), resulting in a heterodimer (PMID:18988809, PMID:21037589). This property can be used to bring together two tagged proteins of interest in vivo in a light-dependent manner, for example to reconstitute a functional protein by bringing together complementary split system components, or to target a protein of interest to a particular subcellular location.