The there are many reasons why the Apple iPhone 4 is proven to be the most successful product launch to date for the manufacturer.  Not only is it the worlds slimmest phone at 9.3 mm, but it also boasts the highest screen resolution of any mobile phone at 640x 960.

Looking at the spec list will make any one realise that the iPhone 4 is something very special indeed.

The handset measures 115.2x 58.6x 9.3 mm, it is surprisingly lightweight at 137 g.  It is arguably one of the most aesthetically pleasing phones available, its popularity no doubt testament to this.  The screen is capable of displaying up to 16 million colours, resulting in awe-inspiring display of the on screen imagery, be it photos, high definition video or games downloaded from the AppStore.  A built-in accelerometer sensor means the contents of the screen can be viewed in both portrait or landscape forms simply by rotating the phone.

Vibration and ringing are utilised to alert users to incoming calls and messages, along with other alert types such as emails and notifications from social networking apps such as Facebook.  There is the added bonus of assigning MP3 files as ring tones, which can be downloaded from iTunes, either directly via the phone, or when the handset is plugged into a computer with the USB connection.

The basic model of the iPhone 4 offers 16 GB of on board storage, which is more than most Smartphones out there.  There is also a 32 GB version, so even the basic model eliminates the need for a microSD card or any expandable storage.  Users are able to store thousands of files within the handset be they music tracks, download apps or any other data.

A fantastic Internet browsing experience is assured with the iPhone 4.  In areas with 3G coverage, an HSDPA connection allows browsing speeds of up to 7.2 Mbps; however a faster and more reliable connection can be attained by utilising Wi-Fi connectivity.  This takes advantage of local wireless networks whenever users have access, be they in commercial, domestic or public locations.  Additional features include Bluetooth and USB, the latter of which allows users to connect the handset to a computer, whereby they can carry out a multitude of tasks via iTunes.

An impressive 5 mega pixel camera is located on the back of the handset, and not only shoots high quality still images, but also high definition video footage in 720p quality.  There is an additional camera on the front of the handset which allows video calling to take place between other iPhone 4 users over Wi-Fi Networks.

The iOS  4 operating System Works in conjunction with a 1GHz Apple A4 processor (the same processor used in the iPad) to provide a lightning fast and highly customisable user experience.  The operating system allows users to download additional apps from the AppStore, of which there are thousands of choices from numerous categories.

Thanks to its high levels of customisation and advanced technology being made available to the masses, it is no surprise that the iPhone 4 is proven so popular.  With a spec list like this, and it looks set to remain successful for a very long time indeed.