The first edition of Crush Step 1 was conceptualized, designed, and created by medical students, then edited by experts in their field, with the goal of being the best resource on the market for truly understanding the material that is tested on the USMLE Step 1. Our research showed that students were frustrated because review books were either too in-depth for the purposes of the test or too focused on memorization rather than understanding. We asked students like you before and after the test what they wish they would have had during their own preparation, and we sought to provide that for future students. This book has always been driven by what those preparing for the USMLE Step 1 want, and this concept has not changed as we took your feedback into account for this edition. The response to the first edition has been overwhelming, and we are truly privileged to be able to bring you a second edition of this text and take into account all of your feedback and requests. When students understand the concepts of how anatomy, physiology, pathology, and pharmacology interact with one another, medicine becomes less about memorization and more about truly learning how the body works – and doesn’t work! The second edition builds on the careful analysis and planning that went into creating the first edition, adding improved explanations and new information important for the USMLE Step 1 based on your feedback. We sincerely hope you enjoy Crush Step 1. Continued feedback is always important to us. This is your book, and we want to make sure everything is clear, precise, and up to date and serves your needs. Although we have a rigorous editing process, it is possible that errors occur within the text. Please help us with our goal to make this text the best resource available for medical students by submitting any comments, suggestions, or corrections to our Facebook group https://www.facebook.com/CrushStep1/ where you can post, message the authors, and see the most up-to-date errata. If you do not use Facebook, you can also e-mail us at CrushStepOne@gmail.com.