iMac has always harnessed the latest technology - and taken it further - to make the ultimate all-in-one better and better. And the Retina display is a testament to that. We pushed the limits of pixel density so you can see everything with pinpoint accuracy. We questioned every method of integrated design to achieve a remarkable level of fit and finish. The result? A beautiful, impossibly thin display of colour and contrast - and zero compromise. Every millimetre of the Retina display was designed, engineered and built to the most exacting standards. Something that 14.7 million pixels makes exceedingly clear. As does a 1.4mm thin display panel designed around the human eye - so every interaction feels as natural as can be. It's that attention to detail that inspired the all-new 21.5-inch iMac with Retina 4K display. And just like the Retina 5K display, it delivers a larger colour palette with more accuracy. Many of the brilliant, unique colours you see in the real world never make it to your screen. A wider colour gamut makes more of these real-life colours available on the Retina display. A striking 25 per cent more. So whether it's a sunset at the beach or your favourite football team's shirts, you'll see them just as you saw them - on a display that's more vibrant than ever. Engineering the Retina display involved the precise calibration of 23 layers that make up a display panel that's just 1.4mm thin. And out of that process we made advancements to improve not only the resolution but also the quality of the entire iMac display. So in addition to the incredible detail, you'll see blacker blacks, more vivid colours, and images that practically jump off the screen.