Michael Steil gave a presentation of reverse engineering of the MOS 6502 processor. Because there are no original schematics or a good descriptions of the 6502 the only way to get the information was to photograph the chip in very high resolution. From the pictures they made a schematic. The schematic was converted to a computer program that can emulate all transistors in the 6502. You can watch the whole 60 minutes presentation on Youtube.