Abstract: The present invention relates to a portable, self-contained, neonatal intensive care unit (NICU) providing heating (or cooling) for the patient by controlled exchange of thermal energy between a transparent enclosure that houses the infant and an internal reservoir. The invention has no requirement for electrical power. The internal reservoir utilizes water that is heated (or cooled) by an external source. The micro-environment inside the transparent enclosure for the infant and the water inside the internal reservoir are thermally and acoustically isolated in order to minimize heat and sound exchange with the ambient environment.