Different lights do make me strange, thus into different sizes I will change

Answer: pupil

More Difficult Riddles with answers

More Difficult Riddles

Different lights do make me strange, thus into different sizes I will change. What am I?
Do what he says and you'll be fine, don't and you lose the game.
Do you know what you can hold without ever touching it?
Don't do this in the shallow end.
Draw four rectangles on a piece of paper. Put nine x's in the four rectangles so that there is an uneven number of x's in each rectangle.
During the 1800's these turned women into hourglasses and is becoming more popular again these days
Each of these ends in a kettle full of precious metal and the double variety is quite awesome
Eight years ago, Bill was eight times the age of his son Bill Jr. Today, if you add their ages together, they add up to 52. How old are Bill and his son?
Everyone has it and no one can lose it, what is it?
Fatherless and motherless. Born without sin, roared when it came into the world. And never spoke again.
Find an English word that uses all of the following letters: PNLLEEEESSSSS
Find an English word which is singular, add an "s" and it becomes plural, and add another "s" it becomes singular again. What is it?