A consequence of doing useful work with computers is the production of heat. Every watt of energy that goes into a computer is converted to a watt of heat that needs to be removed, or else the computer will melt, burst into ames, or meet some other undesirable end. Most computer systems in data centers are cooled with air conditioning, while some high-performance systems use contained liquid cooling systems where cooling uid is typically piped into a cold plate or some other heat exchanger. Immersion cooling works by directly immersing IT equipment into a bath of cooling uid. The National Security Agency’s Laboratory for Physical Sciences (LPS) acquired and installed an oil-immersion cooling system in 2012 and has evaluated its pros and cons. Cooling computer equipment by using oil immersion can substantially reduce cooling costs; in fact, this method has the potential to cut in half the construction costs of future data centers.