mEos2 is a fluorescent protein that can be irreversibly photoconverted from an initial green fluorescent form to a red fluorescent form upon UV irradiation. The green fluorescent form has an excitation peak of 506nm and an emission peak of 519nm, while the red fluorescent form has an excitation peak of 573nm and an emission peak of 584nm in vitro. mEos2 is an artificial derivative of the naturally occurring fluorescent protein encoded by the Lobophyllia hemprichii EosFP gene (GenBank:AY765217), obtained by mutagenesis of mEosFP, containing the additional mutations N11K, E70K, H74N and H121Y relative to mEosFP (PMID:19169260).