Sometime back, Hinnerk Schulz‑Hildebrandt, a biomedical optics engineer at Harvard Medical School, stumbled on something odd while checking a flight map on his phone. As his eye followed the flight ...

You're introduced to someone and your attention catches on their eyes. They might be a rich, earthy brown, a pale blue, or the rare green that shifts with every flicker of light. Eyes have a way of ...