This text has been written for students and professionals who want to learn more about biological rhythms and the science of chronobiology. It is not a comprehensive treatise, but a primer that serves to introduce individuals to a this topic that encompasses all living organisms. It is intended to cover a basic cross-section of the field of chronobiology clearly enough so that it could be understood by a novice, or an undergraduate student, but that it would also be sufficiently technical and detailed for the scientist.