team of MIT chemists have created a carbon nanotube 'lead' that can be used to draw freehand electronic circuits using a standard, mechanical pencil. In a normal pencil, the lead is usually fashioned out of graphite and a clay binder. Graphite, as you may already know, is a form of carbon that is made up of layer after layer of the wonder material graphene. When you write or draw with a graphite pencil, a mixture of tiny graphene flakes and clay are deposited on the paper, creating a mark. (Incidentally, pencil leads never contained lead; it's just that when graphite was first used in the 1500s, they thought it was lead ore, and the name stuck). With MIT's carbon nanotube pencil, the lead is formed by compressing single-walled carbon nanotubes (SWCNT), until you have a substance that looks and behaves very similarly to graphite. The difference, though, is that drawing with MIT's pencil actually deposits whole carbon nanotubes on paper - and carbon nanotubes have some rather exciting properties.In this case, MIT is utilizing the fact that SWCNTs are very electrically conductive - and that this conductivity can be massively altered by the introduction of just a few other atoms, namely ammonia.