Take, for example, the Apple iPhone 4S. Looking beyond the plastic enclosures, the LCD screens and the cameras, there are hundreds of surface mount board level components needed to build just one iPhone 4S including capacitors, transistors, diodes, LEDS and magnetic components. Some are needed for RF purposes, some for switching, and others for power management. Even more components are needed for memory and app processing.
In all, this list is not much different from the requirements of past iPhones or other smartphones however, the size of the components and the vast array of components required will never cease to amaze us!