We sweat on hot summer days. One may think this response is uncomfortable; however, sweating response plays a pivotal role in the regulation of our body temperature and thus is important function for human being. Early studies employed in vitro models to elucidate the mechanisms underpinning sweating. However, the results obtained from in vitro models do not necessarily mirror sweating responses occurring in humans in vivo. This review will introduce in vitro sweat gland studies and review recent in vivo human studies aimed at delineating the mechanisms of sweating.