The iPhone has been Apple's flagship product since its inception in early 2007. Having spent around 150 million dollars, filing more than 200 patent applications, and purchasing for a measly 1 million dollars, one wouldn't expect it to be anything less. Since then it has taken the world by storm with record sales not just for the device itself by also with Apple's innovative App Store. Over the past few years the iPhone has undergone significant changes, evolving into the technological feat it is today. There have been a total of 4 models released since 2007, the original iPhone, the iPhone 3G, the iPhone 3GS, and the iPhone 4. The first iPhone was a revolution in itself since it came with the novelty of a touch screen. No phone at the time had the capability of swiping a toggle button on or off or pinching an image to zoom in and out. The general population of phones was cluttered with buttons that took too much space and were prone to mechanical damage. The iPhone on the other hand didn't have those pesky buttons. Consequently, it had a larger screen compared to other phones, increasing its appeal. The following year Apple released the iPhone 3G. Coming in slightly thicker than its predecessor, it was a huge jump in terms of features. It included a GPS component, an accelerometer, a proximity sensor, and an ambient light sensor; thus paving the way for creating applications with limitless potential. The main feature upgrade, however, was its support for 3G telecommunications, hence its name. This provided users with increased bandwidth enabling more media-intensive applications. Aesthetically, the iPhone 3G has a modified back with a shiny plastic sleek look replacing the outdated plastic black and metallic hybrid. This change was meant to increase the strength of the GSM signal. One downside of the phone was its significant degradation in performance when running iOS 4. To fix that, the user needed to revert back to iOS 3 which was a mean feat in itself! And when you thought it couldn't get any better, in 2009, Apple decided to unleash the next iteration of the smartphone, the iPhone 3GS. Armed with a faster processor and support for faster 3G speeds, the iPhone 3GS was like flicking the sports mode switch on the iPhone 3G. It was smoother and responded a lot snappier than its precursor when running iOS 4. To supplement these improvements, it also doubled the RAM, increased the camera resolution, added native video recording support, doubled the storage space, and employed a fingerprint-resistant oleophobic coating on the touch screen. The most recent model of the phone is the iPhone 4. Released mid-2010, it is significantly thinner than the 3GS. This hardly made any sense since it came equipped with double the RAM, a faster A4 processor, a higher resolution camera with 720p video recording and a flash, a three-axis gyro, a front-facing camera, and an additional microphone at the top of the device for noise cancellation. But as you know with technology, everything gets smaller and thus allows more things to fit in tighter places. One noticeable improvement of the phone is the incorporation of Apple's Retina Display. It has a spectacular 960 by 640 resolution making it the highest resolution screen for any phone out in the market today. The body of the phone was also redesigned to take a flattering look and the screen reinforced with aluminosilicate glass. It is also framed by a stainless steel structure that acts as the antenna. Early adopters found there were signal strength issues when holding the phone a certain way.