No.2 pencils are widely used, but you may not know what the number actually refers to. This video explains how pencils developed into their modern form and the significance of the labeled numbers.

Inside a two-story warehouse, unadorned but for a 25-foot-long No. 2 pencil painted on the outside ... The late 19th century brought the ubiquitous yellow pencil—made in imitation of a posh ...

The marketing behind the yellow pencil In 1888 ... pushes the ink down the pen. Pencils are no longer used in space either, because the graphite (the bit that makes marks on the page) in pencils ...