C-EYFP corresponds to a C-terminal portion (residues 155-238) of the EYFP fluorescent protein. If the C-EYFP split fluorescent fragment is brought together with a complementary split fluorescent fragment in vivo, a functional fluorescent protein may be reconstituted. C-EYFP is designed for use in the bimolecular fluorescence complementation (BiFC) technique, which is used to study protein-protein interactions in vivo (PMID:11983170).