It's been just over eight years since Apple released its first iPhone, and it even seems longer than that considering how much it is credited with changing the landscape of mobile phones.

The iPhone 6S represents the eighth generation of the famed smartphone. But how far has it come in those years? What's changed in design and specs and have the older models held their own over time?

The first iPhone, out in 2007, might look a little rounded and bezel heavy compared to more recent phones, but it still looks good. In true Apple design style it's managed to stand the test of time, which most gadgets fail at within a year or two. A testament to Apple design smarts.

But, to avoid blowing the Apple trumpet too much, the company has played it relatively safe over the years. In reality there have only been a few major changes to iPhone design that stand out. From the first rounded phones to the squarer iPhone 4 then the jump again going back to a more rounded design in the iPhone 6. Everything in between has been either internal or incrementally different.

The major size jump didn't arrive until the iPhone 6 with its iPhone 6 Plus sibling. Other than the iPhone 5 and 5c this was the only time two variants of iPhone have been available.

So let's take a look at the iPhone's walk from hunched simpleton to tall genius.

The original iPhone 

The iPhone 3G

The iPhone 3GS

The iPhone 4

The iPhone 4S

The iPhone 5

The iPhone 5C

The iPhone 5S

The iPhone 6

The iPhone 6 Plus

The iPhone 6S...