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: looking at bright objects has a negative impact on the eyes. 
Sentence2: Looking at bright objects have a negative impact on the retina.

A: bright
****
Q: Sentence1: hunting requires seeing prey. 
Sentence2: hunting requires seeing an animal.

A: hunting
****
Q: Sentence1: an electron microscope is used for seeing very small objects by making them appear bigger. 
Sentence2: Microscopes that use electrons rather than light are called electron microscopes.

A:
electron
****