Thermophotovoltaics (TPV) is concerned with the application of photovoltaic diodes to harvest electricity from thermal radiation. This is achieved through the use of appropriately designed thermal emitters which are typically heated to temperatures of more than 800 ° C. Merits of thermophotovoltaics include the prospect of delivering high power density compared to solar photovoltaics, fuel versatility, portability and capability of around-the-clock operation. The key challenges en route to commercialization of TPV technology include low heat-to-electricity conversion efficiency, mechanical and thermostructural reliability at high temperatures, and cost. Recent advances which include the development of photonic crystal emitters, miniaturization of TPV systems, and improvement of rare earth oxide emitters have contributed to enhancing the performance of TPV systems. Further, current research on ultra-low bandgap photovoltaic materials, thin film monolithic system design, and global system optimization promise additional advances. This article presents an overview of the fundamental principles of thermophotovoltaics followed by a review of the development of all the main components comprising combustion thermophotovoltaic systems. This review also scrutinizes state-of-the-art developments, discusses the fundamental and technical challenges facing commercial adoption of TPV, and prospects of TPV.