The modern tattoo machine is primarily a motor attached to a tube that contains a bar with a needle arrangement on the end. The motor pushes the needle up and down, up to three thousand punctures per minute. The depth is set very shallow, just down into the dermis layer, and the ink runs into the hole from the fountain-pen like tip of the tattoo machine. All of these little 'ink dots' that are in your skin make up the picture. Homemade tattoos, often done with single needles, leave teeny dots and it makes hundreds of punctures with a steady hand to get a clear line. Tattoos that get infected while healing are left with blotchy white areas where the ink heals out and you will have to get the tattoo redone or touched up to fix the damaged areas.