The Human Printer, founded by Louise Naunton Morgan, is a group of artists who uses markers to emulate the printing process. The group reproduces photos by painstakingly ‘printing’ images by hand - dot by dot – in CMYK or B&W to recreate the halftone printing effect of conventional printers.
As explained on the site, The Human Printer assumes the role of the machine and is therefore controlled and restricted by the process of using CMYK halftone created on the computer. The site even goes as far as to list other Human Printer "models," providing a short description of each one's particular printing style and character traits.
You have to give credit to these guys for their huge patience.