Since it launched five years ago, PLOS ONE has redefined the scientific journal. The broad publication criteria and lack of page limit allowed PLOS ONE to grow at a rate never seen before in the industry, to a level where it needed its own category: the Megajournal. Recently, other publishers have sought to emulate the success of PLOS ONE with releases of their own megajournals. These new journals all have similar properties: full Open Access, editorial criteria based on sound science and not on significance or impact, fast turnaround, broad scope. In this talk I shall discuss the features of megajournals, their benefits and weaknesses, and what their arrival means for the future of scientific publishing.