Abstract: Laser powder bed fusion is a metal additive manufacturing (3-D printing) process that has become increasingly popular over the past decade. However, the reproducibility of parts manufactured by this process is still a challenge and requires an understanding of the keyhole and melt pool dynamics during the process. This work will highlight the use of high-speed X-ray imaging with high-speed infrared (IR) imaging to study the thermal histories of laser powder bed fusion processes in real time. Using these techniques, we demonstrate the observation of many dynamic physical phenomena that affect the quality of additively manufactured parts as well as characterize the formation of printing defects using the IR signature.