The diamond anvil apparatus, invented nearly 50 years ago, has developed into a versatile tool for a broad spectrum of high-pressure research topics, ranging from low-temperature physics to high-temperature geoscience. It is superbly suited for high-pressure and high-temperature synthesis because new materials can be identified and characterized in situ. The combination of high pressure and high temperature, generated by two opposed diamond anvils and infrared (IR) lasers, respectively, has allowed the simulation of the extreme conditions of planetary interiors, the discovery of new structures and behavior in elements, and the synthesis of novel hard materials. Here, we describe the relatively simple technique of generating and controlling high pressure and high temperature, and present recent examples related to these topics.