The pupil of your eye expands as much as 45% when you look at someone you love!

Have you ever heard the old adage "love is blind." Well true as that my be, it would also be accurate to say something like "love is wide-eyed."

It turns out that your eyes physically react when they see someone that you love or are attracted to. Your pupils dilate when there is less light - to let in more light so that you can see.

Dilated pupils are seen as more attractive. So either your eyes are subconsciously trying to make you more attractive to that person you love or they are dilating simply to be able to take that person in more clearly. What came first, the dilated pupils or the attraction?

(Source)