A method of normalizing a bioluminescent signal detected in a live non-human mammalian animal comprising a bioluminescent protein, the method comprising: providing at least one live non-human mammalian animal, the animal comprising: (i) the bioluminescent protein; and (ii) a composition comprising a bioluminescent substrate and a fluorescent tracking dye, wherein the bioluminescent substrate and fluorescent tracking dye are individual components, the composition having been administered in solution in a buffer by injection between 1 minute and 1 hour prior to imaging, such that the bioluminescent substrate and fluorescent tracking dye are distributed similarly in the animal; wherein the bioluminescent substrate reacts with the bioluminescent protein to generate a bioluminescent signal having a wavelength; wherein the fluorescent tracking dye emits a fluorescence signal of a different wavelength and wherein the bioluminescent substrate is transformed to an excited state in the presence of the bioluminescent protein, oxygen and ATP; measuring the bioluminescent signal generated by reaction of the bioluminescent substrate and the bioluminescent protein from the at least one animal; measuring the fluorescence signal of the tracking dye from the at least one animal: and normalizing the bioluminescent signal to the fluorescence signal of the tracking dye in the at least one animal, wherein normalizing comprises finding an average fluorescence signal and determining a deviation of the fluorescence signal in an individual animal from the average fluorescence signal, whereby if the deviation is greater than about 30% from the average, the animal is re-imaged by discarding and repeating the measurement of bioluminescence. providing at least one live non-human mammalian animal, the animal comprising: (i) the bioluminescent protein; and (ii) a composition comprising a bioluminescent substrate and a fluorescent tracking dye, wherein the bioluminescent substrate and fluorescent tracking dye are individual components, the composition having been administered in solution in a buffer by injection between 1 minute and 1 hour prior to imaging, such that the bioluminescent substrate and fluorescent tracking dye are distributed similarly in the animal; (i) the bioluminescent protein; and (ii) a composition comprising a bioluminescent substrate and a fluorescent tracking dye, wherein the bioluminescent substrate and fluorescent tracking dye are individual components, the composition having been administered in solution in a buffer by injection between 1 minute and 1 hour prior to imaging, such that the bioluminescent substrate and fluorescent tracking dye are distributed similarly in the animal; wherein the bioluminescent substrate reacts with the bioluminescent protein to generate a bioluminescent signal having a wavelength; wherein the fluorescent tracking dye emits a fluorescence signal of a different wavelength and wherein the bioluminescent substrate is transformed to an excited state in the presence of the bioluminescent protein, oxygen and ATP; measuring the bioluminescent signal generated by reaction of the bioluminescent substrate and the bioluminescent protein from the at least one animal; measuring the fluorescence signal of the tracking dye from the at least one animal: and normalizing the bioluminescent signal to the fluorescence signal of the tracking dye in the at least one animal, wherein normalizing comprises finding an average fluorescence signal and determining a deviation of the fluorescence signal in an individual animal from the average fluorescence signal, whereby if the deviation is greater than about 30% from the average, the animal is re-imaged by discarding and repeating the measurement of bioluminescence.