Abstract: There is a need for a broadly applicable, strain non-specific, bioluminescent imaging tool that will enable researchers to study a ?-cell mass in the context of development, disease or transplantation. The disclosure, therefore, encompasses embodiments of a method of identifying a non-diabetic pancreatic ?-cell, the method comprising the steps of: delivering to a pancreatic ?-cell a composition comprising a coelenterazine; allowing the ?-cell to generate a coelenterazine-dependent bioluminescent signal; and identifying the cell as a non-diabetic pancreatic ?-cell by detecting the emitted coelenterazine-dependent bioluminescent signal.