Lithography.

Lithography is a very complex print style.  It is basically a form of intaglio in which a smoothed limestone block is "masked" with a wax agent which repels ink onto the paper.  This is a very lengthy process that is rarely done any longer.  However, the more modern way of doing this is done on aluminum sheets coated in a plastic which basically works in the same way.

I personally have never done this method.  I have heard through old professors that the method for smoothing the limestone by itself takes tens of hours to complete.  

It is, however one of the most durable print methods.