Molecular and cellular biology is the study of cellular ultrastructure and function. Current research in immune regulation, delineation of receptor control function (signal translation at the cellular level), and nucleic acid manipulation (genetic engineering) illustrates fundamental relationships among biochemistry, immunology, and molecular and cellular biology. Our knowledge already includes significant discoveries in membrane permeability, ionic gradients, and mediators of homeostasis. To these are added newer discoveries in bone metabolism, vascular anatomy and physiology, trace element deficiency, and the broader field of nutrition. Biochemical research gradually is unlocking the mysteries of otosclerosis, Paget's disease, endolymphatic hydrops, ototoxicity, acoustic trauma, presbycusis, and other forms of sensorineural hearing loss. This paper presents some of the research topics of current interest. Relationships of molecular and cellular biology, immunology, and nutrition are discussed. Molecular and cellular biology of the inner ear is an exciting “new” frontier.