Water is essential for life and a major key for survival. It is originated
mostly from drinking, feedstuffs, and metabolic pathways (metabolic water). Water
comprises from 75% body weight in infants to 55% in the elderly and is essential for
cellular homeostasis. Thirst and water consumption are centrally and peripherally
regulated by complex and tightly interconnected mechanisms. This chapter summarizes
current progress and knowledge associated with body fluid homeostasis and the
regulation of water intake at the central and peripheral levels.
Keywords: Central circuit, ncRNA, Osomoregulation, Peripheral pathways, RAAS, Thirst, TRPV, Water intake.