All blue-eyed people have one ancestor in common, born around 6,000 to 10,000 years ago. Blue eyes are caused by a gene mutation. For years, researchers had searched for it on the OCA2 gene.

From eyes the size of a dinner plate to 360-degree vision ... Rods are light-sensitive cells, and cones are sensitive to colour. These squid have one small, blue eye and one large and yellow, bulging ...