Take a moment and envision an electromagnet: a simple coiled wire driven by a hefty electrical current gives a fully-programmable magnetic field strength (on, off, and everything between).  Electromagnets are ubiquitous, but it turns out that there is a little-known device with similar functionality yet zero static power consumption -- they are called electropermanent magnets, and they've been around and in use since the 1960's!  A 2010 PhD thesis by MIT Media Lab's Ara Knaian examines the physics, scaling, trade-offs, and several new actuator designs (eg. stepper motors) using these little-known wonders.  Recently, electropermanent magnets facilitated an innovation in "programmable matter," where they were instrumental in creating the world's smallest self-contained modular robots to date (12mm/side).  Read on for details about this fascinating technology, along with discussions about existing and possible robotic applications.