Until March 16, 2013, the U.S. has a “first to invent” patent system. That is, if two or more patent applications are filed for the same invention, any patent on that invention is awarded to the applicant who can show the earliest date of invention. Proof of invention must be in the form of documentary evidence, and the best form of this evidence is a laboratory notebook. The purpose of a lab notebook is to document how and when inventions occur, and to show what steps are taken and by whom. A lack of documentation can result in the loss of patent rights if the date of an invention is challenged, or if the inclusion or exclusion of a particular inventor is disputed. For these reasons, the UW C4C advises researchers to develop good record keeping practices.