Pupils are the dark-colored openings at the center of your eyes that let light in. Doctors can look at your pupils for clues about your health. The size of your pupils and how they react to light ...

A team of researchers from the Department of Clinical Neuroscience, Karolinska Institutet conducted three different experiments to get to the bottom of this mystery.

New research suggests your pupils may reflect how clearly you remember something. Get the Popular Science daily newsletter💡 Breakthroughs, discoveries, and DIY tips sent every weekday.

His gaze softens as he draws closer to you. With one hand around your waist and the other cradling your jaw, he pulls you in. You look into his eyes, and notice his pupils have grown large and hungry.