Cell phones seem to get sleeker and slimmer by the day, and the Apple iPhone 4 is no exception. Its new design attracts the eye, a design that is appreciably thinner than the iPhone 3GS. Whereas the iPhone 3GS is 12.3mm thick, the iPhone 4 is only 9.3mm deep for a reduction in size of about 24%. Additionally, the iPhone 4 is narrower, measuring 59mm to 62mm. The weight of the iPhone 4 has stayed the same as its predecessor at 136g, but the dimensional alterations lead to a less bulky perception. Changes in design are of course just the tip of the cell phone iceberg. Where the Apple iPhone 4 really shines is in the technological department. After all, beauty is only skin deep. Maintaining the 3.5-inch display of the iPhone 3GS, the iPhone 4 doubles the resolution of its display to 960 by 640 pixels. The IPS display is comprised of 326 pixels per inch, making it the highest resolution phone available. The new 'Retina' display, so called because it is made up of more of pixels than the human retina can process, significantly improves the sharpness and clarity of images. The phone's screen also uses the same in-plane switching (IPS) techniques as are used on the screens you will find on iMacs and iPads. Consequently, not only is the display bright and colorful, it has a massive viewing angle, meaning that it looks great no matter which way you hold it or which angle you are looking at it from. The iPhone 4 uses Apple's A4 processor, which is the same one that was chosen to power the iPad, and it runs the newly developed iOS 4 operating system. As a result of this OS, the phones capabilities are much better. Previous owners of iPhones will be pleased to hear that multitasking is one of the new capabilities. It feels long overdue but, as with Apple's long-awaited cut-and-paste feature, it meets, and even exceeds, expectations. Camera and video advancements are also welcome enhancements to the iPhone 4. The primary camera has received a boost from 3 to 5 megapixels. This is accomplished with the same size pixels. Also new is an LED flash, backlit sensor and a 5X integrated zoom. High-def video is now possible at 720p and 30 frames per second. The tap-to-focus feature previously found only on the camera is now included on the video recorder. To summarize, the Apple iPhone 4, is a must-have for any smartphone lovers. Unlike the previous upgrade (from the iPhone 3G to the 3GS), which saw only slight performance improvements, the iPhone 4 sees significant improvements all round, making it comprehensively better than anything that we have seen before.