Mummification took about 70 days. The body had to be dried out, and then ritiually anoited with oils and perfumes. Later, all of the body's organs were taken out. 

The Canopic Jars were just for this purpose. They would hold what the Egyptians considered the most important organs: The Stomach, the Intestines, the Lungs, and the Liver. The heart, considered the most important organ, was left inside the body, or at least had a placer for the heart.

Ironically, the brain was considered useless and tossed out!

This was done to give the spirit a vessel to stay in while they journeyed through the afterlife. It was considered, if they didn't become a mummy, that they had no body in the afterlife. 

That's gross. What got mummified?

Mostly people. However, cats and bulls, considered sacred animals, were often mummified.