History of Orexin Research -- The Hypocretin Story -- Input and output systems of orexin neurons -- Physiological roles of orexin receptors on sleep/wakefulness regulation -- Orexin receptor functions in the ascending arousal system (Folder name - Leonard) -- Elucidation of neuronal circuitry involved in the regulation of sleep/wakefulness using optogenetics (Folder name - Yamanaka) -- Modulation of thalamocortical pathways by orexins -- Orexins, Alcohol and Sleep Homeostasis -- Orexin induced modulation of REM sleep and its loss associated patho-physiological changes are mediated through locus coeruleus -- Role of orexin on sleep: interactions with other neurotransmitter systems.