IFP2.0 is a monomeric infra-red fluorescent protein with an excitation peak of 690nm and an emission peak of 711 nm in vitro. It is an artificial derivative of the bacteriophytochrome encoded by the Deinococcus radiodurans BphP gene, obtained by mutagenesis of IFP1.4. In order to fluoresce, IFP2.0 requires a biliverdin cofactor to act as the chromophore. This can be supplied in a transgenic animal by including a transgenic construct that encodes a heme oxygenase (HO) (FBrf0225053).