While Snapchat struggles to nab more users, Instagram is steaming ahead the only way it knows how: By copying Snapchat. The Facebook-owned service is adding a feature to its (vastly more popular) take on Stories that's all about throwbacks. The update essentially allows you to add pics and videos to your Story that are more than 24 hours old -- a function that was oddly amiss in the past. That way, the entire camera roll is available for your disappearing #FlashbackFridays posts.