Nanoblock hit the scene - i.e. the Japanese toy market - in October 2008. Manufactured by Kawada Co. Ltd, they are miniature versions of their Diablock plastic construction bricks. According to Wikipedia they use a dividing flange instead of a tube, apparently making them totally different to that other famous building brick...
Still, they totally work as mini Lego , although they're really more like Duplo size in 1/6 scale. As you can see it doesn't impact on them looking cool!
There are so many sets out there to collect. (Seriously, sooo many.) But one set should do you for all your miniature needs. My advice is to get one with a good variety of brick colours - above you see the innards of the red and green macaw [NBC-034] - for which you can expect to pay about £5. Bargain, eh? :)
You can see the other 'mini' sets available at the Diablock website. You can also get 'sights to see', advanced, basic add-on, and gift sets. Here are a few of my favourites: