It had previously been uncovered that Hillary Clinton was taking use of a private email account whilst serving as the US Secretary of State from 2009 to 2013 - people in these positions are historically asked to use their officially supplied email accounts for reasons including transparency and security.
On her official Twitter page, Clinton claims she has nothing to hide, stating "I want the public to see my email. I asked State to release them. They said they will review them for release as soon as possible."
This was then followed by a statement from the State Department whom warned users of this tedious process "The State Department will review for public release the emails provided by Secretary Clinton to the Department, using a normal process that guides such releases. We will undertake this review as soon as possible; given the sheer volume of the document set, this review will take some time to complete."