Marine mammals comprise some of the most highly adapted mammals, many with unbelievable diving capabilities, high intelligence and complex social behaviour, and some with brains larger than that of humans. Many possess echolocating and communication skills that we are only beginning to understand. This work brings together a group of experts focused upon cell and molecular biology of aquatic mammals. Methods currently being used to explore marine mammal biology are discussed, such as genetic tracing of subpopulations of whales and seals by DNA fingerprinting, use of immune system molecular markers, cell culture and ELISA techniques, and electron microscopy.