mEosFP is a fluorescent protein that can be irreversibly photoconverted from an initial green fluorescent form to a red fluorescent form, upon near-UV irradiation of approximately 390nm. The green fluorescent form has an excitation peak of 505nm and an emission peak of 516nm, while the red fluorescent form has an excitation peak of 569nm and an emission peak of 581nm in vitro. mEosFP is an artificial derivative of the naturally occurring fluorescent protein encoded by the Lobophyllia hemprichii EosFP gene (GenBank:AY765217), containing the mutations V123T and T158H. mEosFP is largely monomeric, but has a tendency to dimerize at high concentrations (PMID:15505211).