User: What are the key features introduced by Apple in their iPhone since its creation which makes it so popular and innovative?
Assistant: The iPhone was the first mobile phone with multi-touch technology. Since the iPhone's launch, it gained larger screen sizes, video-recording, waterproofing, and many accessibility features. Up to iPhone 8 and 8 Plus, iPhones had a single button on the front panel with the Touch ID fingerprint sensor. Since iPhone X, iPhone models have switched to a nearly bezel-less front screen design with Face ID facial recognition, and app switching activated by gestures.