While Mark Tilden spends a lot of his time building toys these days, he hasn't stopped working on serious projects. His latest work for DARPA is described in a new article from SmallTimes. His newest creations are called Cohesive Elemental Arrays (CEAs) but are usually referred to as Nano-legos. CEAs are tiny solar-powered robots that act together in groups to form structures. With the help of his new friends in the toy industry, Tilden hopes to move to micro-sized CEAs and eventually nano or atomic scale CEAs.