Generate an overlapping word between the given two sentences. When you find the overlapping words, they don't have to match exactly, e.g., "survival" and "survive" are valid overlapping words. Little words like "the" or "of" don't count! You must generate significant words which are not the stop words.
Q: Sentence1: microscope is used to see small things by biologists by making them appear bigger. 
Sentence2: Biologists study small things that can't normally be seen with an unaided eye.
A: 
small