Histology is the discipline of biology that involves the microscopic examination of thin stained tissue sections in order to study their structure and correlate it with function. Histology can detect signs of disease not easily recognized on gross examination and can therefore be of interest in fish health supervision. The aim of this volume is to present a general reference guide providing an extensive set of histological images of fishes (about 40 species). This atlas is designed for use by students and researchers, biologists, ichthyologists, fish farmers, veterinarians working in fisheries and, of course, by comparative histologists who want to learn more about the fish world.