Every form of electric lighting produces an unwanted by-product: heat. In the case of incandescent and fluorescent lighting, generations of engineers have developed ways to minimize and/or divert heat from luminaires and fixtures. But LED lighting, appearing today in growing quantity and variations, poses new and different challenges. Heat buildup can reduce an LED’s light output and cause a color shift and at the same time, shorten the component’s useful life. It has been said that thermal management is by far the most critical aspect of LED system design. From an engineer’s perspective, this may mean learning to work with tools and procedures that go beyond the comfortable realms of mechanical and electronic design. Fortunately a host of thermal design solutions is ready to help simplify the engineer’s journey through thermal validation and measurement challenges.