Sometime, if you want to remind your self to follow up about email that you received, you might mark the email as unread. However, when you receive more than 300 emails a day, the unread email can be easily buried.
Thankfully, gmail can display all unread email in box. How? In the search box at the top of the page, type the following:
label:(unread inbox)
Then, click search. All of your unread emails will be displayed.