How are really small mill bits made?

We've recently been milling with some 1/64th bits and we have bits as small as .006" that we use on occasion. We've also done drilling with bits as small as 300 microns!

These bits have to have features on the scale of microelectromechanical systems, but seem to have been made using conventional methods. How on earth are they made? Especially with such amazing accuracy?!

Thanks!