Ok so I know this is the Lego forum officially, but as a lifelong Lego fan I thought I'd share this as I only discovered them recently. I was in Dundrum SC (gadget shop - can't think of name) the other week and saw Nanoblocks for the first time. A MUCH smaller version of Lego which I think originates in Japan. They have some really interesting models of things around the world like Eiffel Tower, Space Station, Maoi Statues, etc etc. The bricks are absolutely tiny so you need to be careful opening packs of them, plus tricky enough to work with given the size and the instructions are shorter and therefore a little more complicated that Lego! I got the Moai Statues and they were interesting to build. Although the bricks are smaller in a way I think it's kinda like an adult Lego!
I think original Japanese website
UK Promotional Website