Complex sentence: She took Max's pencil, which Max had been chewing on, placed the saliva collected from the pencil tip on a slide and examined the slide through a microscope and she could see that his cells were not human.
Split into simpler sentences: She took Max's pencil, which Max had been chewing on, placed the saliva collected from the pencil tip on a slide and had a look at the slide through a microscope. When she looked under the microscope she could see that his cells were not human.