So what does it mean then? I am very interested to know.
"An electron microscope is a type of microscope that produces an electronically-magnified image of a specimen for detailed observation. The electron microscope (EM) uses a particle beam of electrons to illuminate the specimen and create a magnified image of it. The microscope has a greater resolving power than a light-powered optical microscope, because it uses electrons that have wavelengths about 100,000 times shorter than visible light (photons), and can achieve magnifications of up to 2,000,000x, whereas ordinary, non-confocal light microscopes are limited to 2000x magnification."
Wikipedia is your friend 
As for what it means; as I alluded to earlier it's quite common practice to add false colour to images obtained by electron microscope. Grayscale is boring.
Sign up with Google
