OMG - these micro-sized nano blocks are the hottest thing since Lego! With over 150 assorted size and colored pieces (most around .25" long and 1/8" tall), watch in amazement as this koala bear takes shape. Includes detailed color instructions. Definitely not designed for children under the age of 8 years. I'm telling you - these pieces are really tiny (I couldn't do it)! From 1 to 5, the level of difficulty on this one is a 3 - with "5" being most difficult.