This document discusses inter partes review (IPR) of patents. It begins with an overview of traditional options for challenging patents such as litigation and reexamination. It then provides details on IPR, including that it allows review of patent validity based on prior art under 102 and 103, has a faster timeline than litigation, and has resulted in over 1,000 claims being found unpatentable so far. However, it also notes risks such as claims being amended and estoppel preventing the same invalidity grounds from being raised again.