miRFP670nano is a monomeric near-infrared fluorescent protein with an excitation peak of 645nm and an emission peak of 670nm in vitro. It is an artificial derivative of the naturally occurring fluorescent protein encoded by the Nostoc punctiforme NpR3784 gene. It is a 147 amino acid residue protein based on the NpR3784 GAF domain, with the N-terminal α1-helix removed and a number of additional mutations introduced during optimization (amino acid substitutions V7M, F25C, M26V, Y27F, P31E, S41A, A48S, N51K, Q55R, T57R, I72Y, G82N, H87Y, N99I, N117H, C119L, L136Q, and Q139V relative to the wild-type NpR3784 GAF domain sequence). In order to fluoresce, miRFP670nano requires a biliverdin (tetrapyrrole) cofactor to act as the chromophore. This can be supplied in a transgenic animal by including a transgenic construct that encodes a heme oxygenase (PMID:30655515).