X-ray tomography has emerged as a powerful technique for studying lithium ion batteries, allowing nondestructive and often quantitative imaging of these complex systems, which contain solid components with length scales spanning orders of magnitude and which are in-filled with liquid electrolyte. Over the past decade, X-ray tomography has allowed interrogation of structure and material composition, providing quantitative or qualitative insight into battery operation and degradation. In this review, we first provide an overview of X-ray tomography and explore what types of experiments can yield insight into open questions in the lithium ion battery research field. In the second half of the review, we discuss the aspects a researcher must consider, and we summarize challenges and approaches to sample preparation, experimental setup, and data analysis. Finally, we describe both outstanding challenges and promise in using X-ray tomography for lithium ion battery research.