Apple's latest operating system, iOS 10, has a ton of fun features which revolutionize texting on the iPhone. The most-talked-about feature is arguably invisible ink, which lets you send obscured texts to people. Some have compared the feature to Snapchat, which lets you send messages that disappear forever after a few seconds. Before you start sending nudes, assuming your messages will disappear into the ether, you need to know how invisible ink works. Be warned.