A lot of people don't know this, but iPhone batteries can kind of explode. You know who didn't know this, this dude who was working at one of those We Can Fix Your iPhone stores. He was playing around with a dinged up phone, and POOF, black smoke everywhere.
In the description for the video, the guy breaks down what happened:
"A customer came into the store with screen damaged iPhone 6+ for repair. The customer wanted repair of broken screen and complained of Apple genuine battery not holding charge. We removed the customer's Otterbox and prepared to book the phone in. Then, the customer picked up phone and applied a regular amount of pressure to the screen, the same as any normal person would do everyday during regular use. The battery failed and exploded. Initial force of the explosion caused the screen to come off the phone. Our staff extinguished the phone with a fire extinguisher. We had to evacuate the store due to fumes and could not open for the rest of the day. Draw your own conclusions, but imagine if this happened five minutes earlier when the guy was driving to the shop and not in the shop."
Yeah, imagine if that guy had taken it out of the case and poked around the battery while driving. Let this be a lesson, just bring it to Genius Bar or don't drop your phone.