Making an optical lens

Having recently got into photography I can admit I have no idea how the device works on a technical basis. I have especially little idea about lenses and how they are made. This video from the Discovery Channel (quality is not great) gives a pretty good rundown of how a lens is made. It is pretty fascinating to see how much is done by hand and not just run through a machine and how many stages there are in the whole process. My favourite part was actually when they showed how they engraved the lens information onto the lens barrel.