The study of sleep is a useful approach to studying the brain in psychiatric disorders and in investigating the effects of psychotropic drugs. Sleep physiology lends itself well to pharmacological and physiological manipulation, as it has the advantage of a functional output, the electroencephalograph, which is common to all mammals, and can be measured in freely moving (or naturally sleeping) animals under controlled laboratory conditions or in a naturalistic home environment. The complexity of sleep architecture varies between species but all share features which are comparable. In addition, sleep architecture is sensitive to changes in brain neurotransmitters such as serotonin, so cross-species sleep measurement can be combined with pharmacological manipulation to investigate the receptor mechanisms controlling sleep-wake regulation and sleep architecture in response to known and novel agents. Translational approaches such as these have improved our understanding of sleep circuitry and facilitated the development of new treatments for sleep disorders, particularly insomnia. This review provides examples of how research findings within the sleep field have been translated between animal models, healthy volunteers and patient populations with particular focus on the serotonergic system.