When creating iPhone 4, Apple designers and engineers didn’t start with a clean sheet of paper. They started with three years of experience designing and building the phones that redefined what a phone can do. iPhone 4 is the result of everything they’ve learned so far. And it’s all contained in a beautiful enclosure a mere 9.3 millimeters thin, making iPhone 4 the world’s thinnest smartphone.

All the breakthrough technology in iPhone 4 is situated between two glossy panels of aluminosilicate glass — the same type of glass used in the windshields of helicopters and high-speed trains. Chemically strengthened to be 20 times stiffer and 30 times harder than plastic, the glass is ultradurable and more scratch resistant than ever. It’s also recyclable.