The document summarizes the transformation of academic publishing from a traditional closed access model to an emerging open access model. It notes that currently there are 25,000 journals publishing 1.5 million papers per year mainly through subscription access, but that open access allows free and unrestricted access and reuse of publications. It highlights PLoS ONE as a pioneering open access megajournal that has grown from publishing 1,200 articles in 2007 to over 14,000 articles per quarter in 2011, becoming the largest journal in the world.