The most incredible thing I have ever seen!! It looks like a normal pen but on closer inspection it has 4 different colours!!! In one pen!!! Science has come a long way since bird feather and blood. How they have managed to cram so much technology in one small bit of plastic I do not know - and don't get me started on the wonders of plastic. With this pen you choose your colour via a small plastic button at the top of the pen. Then when the pen is depressed and moved on a sheet of paper, ink of the same colour appears - incredible. If you make the correct kind of movements you can even make writing appear!! Who needs computers and keyboards with this kind of invention? Anyway, as soon as you want to change colour just slide the button of your colour choice and, hey presto, new colour. Obviously you are restricted to blue, red, green and black, although I did make a dirty brown colour by colouring blue on top of red. Putting it simply I would put it the invention of this pen on par with the invention of the wheel, the computer or the nasal hair trimmer. Quite simply Genius.