X-Mem is a flexible open-source research tool for characterizing memory hierarchy throughput, latency, power, and more. The tool was developed jointly by Microsoft and the UCLA NanoCAD Lab. This project was started by Mark Gottscho (Email: email@example.com) as a Summer 2014 PhD intern at Microsoft Research. X-Mem is released freely and open-source under the MIT License. The project is under active development.We have a research tool paper describing the motivation, design, and implementation of X-Mem, as well as three experimental case studies using tools to deliver insights useful to both cloud providers and subscribers. If you use our tool and publish or otherwise publicly report results, we ask that you please cite the following paper as well as provide a link to our tool homepage (https://nanocad-lab.github.io/X-Mem).