In vivo bioluminescent reporters for small animal non-invasive optical imaging consist of bioluminescent enzymes such as firefly, renilla, gaussia, bacterial and clickbeetle luciferase. Cells can easily be stably transduced with these reporter proteins by means of lentivirus transduction. Substrates are D-luciferin, coelenterazines and caged/cleavable luciferins.  Self-illuminating quantum dots can be used to label cells or tag molecules, peptides and antibodies. Bioluminescent substrates for e.g. beta galactosidase are also available.