Also can stand for Search Engine Marketing (aka those targeted ads you see based on your search history). Although scanning electron microscopes are way cooler.

In physics grad school I got to play with electron tunneling, cool stuff. Also, little known fact, MRI is actually known as NMR, Nuclear Magnetic Resonance, they dropped the Nuclear from the name to make it more publicly palatable. We had to build a basic NMR device in grad lab first year, wicked fun.