Any of several proteins that emit red fluorescent light and are used as markers in cell biology and cell imaging microscopy (see fluorescent protein). The first to be widely used, termed DsRed, was derived from the coral animal Discosoma striata. Following excitation it takes several hours to emit red light, after going through a green phase, which can cause confusion if green fluorescent protein is being used at the same time. Subsequent mutated forms of DsRed, such as DsRed-Express, have improved brightness and given more rapid maturation of the red fluorescence. Another commercially available RFP is HcRed, derived from the coral Heteractis crispa.