Obstructive sleep apnea is an under recognized and under diagnosed medical condition, with a myriad of negative consequences on patients’ health and society as a whole. The most acting reason behind Obstructive sleep apnea given as in literature is due to recurrent episodes of upper airway (UA) collapse during sleep. From the mid-1990s to the present, we have seen an explosion of basic, clinical, and population research directed toward the prevalence, causes, consequences, and treatment of this long-standing, although only recently appreciated, problem. Sleep apnea has attracted a myriad of researchers from diverse disciplines and clinical subspecialties.Finally, given the relatively high prevalence of this sleep-specific problem with potential carryover to daytime pathology, sleep apnea has provided great impetus to the growth of sleep medicine as a clinical and research specialty.