tdTomato is a red fluorescent protein with an excitation peak of 554nm and an emission peak of 581nm in vitro. It is an artificial derivative of the naturally occurring fluorescent protein encoded by the Discosoma drFP583 gene (GenBank:AF168419; AAF03369), consisting of a tandem dimer of the dTomato fluorescent protein linked by a 12 residue linker (PMID:15558047).