Proceedings of the National Academy of Sciences of the United States of America (PNAS) is one of the world's most-cited and comprehensive multidisciplinary scientific journals, publishing more than 3,200 research papers annually. Submissions are accepted from all researchers; authors do not need to have a connection to an NAS member to publish in PNAS. Established in 1914, PNAS publishes cutting-edge research, science news, Commentaries, Perspectives, Colloquium Papers, Reviews, and actions of the NAS. PNAS is available by subscription and all content is free after 6 months. The journal's content spans the biological, physical, and social sciences and is global in scope. Nearly half of all accepted papers come from authors outside the United States. PNAS strives to publish only the highest quality scientific research, and papers undergo rigorous peer review and approval by an NAS member before publication.