The basic centerless grinder design was developed around 1905, though back then the design was much larger and was intended for industrial use processing plant matter. When the design was miniaturized for use in pharmacies, somehow we smokers got our hands on it (possibly passed on by a chill pharmacist), and we’ve been using it to grind up our herbs ever since! At first the design was simple: two pieces, each with teeth and a magnet in the middle. It worked, but it could be improved; with only two pieces, it wasn’t as efficient as possible. Designers added a third piece, and put holes in the bottom of the grinding chamber to enable continuous grinding of herbs. Then they added a fourth piece, and a mesh screen to separate them, and the modern four piece grinder as we know it was born!