The fascination writ large on the children's face of Author's village while observing fireflies (Min Mini Poochi in Tamil) inspired the Author to study bioluminescence in fishes of Family Leiognathidae at the CAS in Marine Biology, Porto Novo,Chidambaram, South India which led to new findings too. Part I of the book is compilation of literature on the luminescent organs of cartilaginous and bony fishes as also deep water and shallow water fishes. Part II is observations on the luminescent system and interspecific variations in the morphology of the luminous gland in six species of Silver Bellies belonging to the genera Gazza, Secutor and Leiognathus of which L. dussumieri and L.berbes are described for the first time. Existence of sexual dimorphism in Silver Bellies, duly supported by morphological studies of luminous glands, is reported. A new Key for identification of different Genera of Family Leiognathidae is suggested. The need for an integrated approach by both biologists and biochemists for better understanding the phenomina of bioluminescence in marine fishes is emphasized. This book would motivate both students and researchers focusing on bioluminescence in fishes.