Apple's iPod, surely one of the coolest gadgets of the 21st Century, celebrates its fifth birthday today.

The iPod - a brand of portable media players designed and marketed by Apple Computer - was first unveiled by Apple CEO Steve Jobs on October 23, 2001. The device was the culmination of work undertaken by a team of engineers assembled by Apple's Hardware chief Jon Rubinstein, who were tasked with designing and building the iPod in less than a year. The result of their work was a Mac-compatible product with a 5GB hard drive that put "1,000 songs in your pocket."

Not everyone believed that the iPod would be a success when it was launched. Some called it "lame" or "overpriced", and indeed the product was one of the "Top Five Worst Tech Gifts for Christmas 2001". But when the iTunes website launched two years later, sales of the iPod rocketed and the brand crossed over from the IT world to the world of fashion. Some 70 million iPods have been sold and of those, 40 million were sold in the last year.

There have been many different types of iPod, including the iPod mini, iPod nano, iPod shuffle and video iPods. Although claiming a vast army of devoted fans, the media players are not without their criticisms; Apple’s perhaps exaggerated claims of battery life and the non-replaceable nature of the batteries being some of them. Recently, a batch of iPods left the factory with viruses on them. Nevertheless, the iPod range of devices remains highly successful worldwide.

Where is the iPod going next? It is a bubble that is set to burst, or will the Apple innovation machine triumph again? What is next for the iPod range – perhaps an iPod mobile phone? Whatever happens, the iPod will surely go down in history as being almost as memorable as the Sony Walkman.