The Proceedings of the 12th International Symposium on Bioluminescence (BL) and Chemiluminescence (CL) contains up-to-date information on the latest developments in BL and CL presented by scientists from around the world.Light-emitting reactions are now a vital component of many key technologies in research and in routine analytical laboratories -- replacing radionuclides in many situations. This volume presents a compilation of the latest developments from key experts and leading-edge researchers in this area.