The characteristics of the personal micro-environment, consisting of the thermal plume, clothing, gap between skin and clothing, and respiration, will be defined. The importance of free convection around the body and its interaction with external flows, clothing and the resulting heat- and mass transfer for thermal comfort and inhaled air quality will be outlined. The benefit arising from measurement and control of the micro-environment, in terms of sensing body physiological signals, improving people’s thermal comfort and inhaled air quality, reduction of exposure to airborne infectious agents and energy saving will be demonstrated by several methods that are applicable in practice.