Storage is similar to communication, except that the displacement of information is a delay in time, rather than a movement in space. You have it now, but will need it later. Information storage is a major element of all living things, and has also been a part of human culture for many thousands of years. Examples of the latter are petroglyphs (picture carved into rock), quipu counting systems used by the Incas and writing. Computers store data using two technologies: electronic or solid state storage, as in USB flash drives, and magnetic storage, as in most hard drives. Students do some experiments with coils and magnets to explore how data can be written to or read from a hard drive, and then relate these methods to the operation of motors, generators and electromagnetic doorbells.