Traditional tattoos are permanent forms of skin art; you make your choice and you stick with it for life. Well, with time comes technology, making those choices a little easier to make.
Electronic tattoos can be done via the insertion of fully programmable nano-tube implants under the skin. You can arrange them into different patterns using electromagnetic fields, thus giving you the ability to change your art at will.
Digital ink tattoos are similar in nature. Electronic fields are used to manipulate the nano-spheres in the ink underneath the skin.