Ninjas used a system called Goshiki-mai, meaning Five Colored Rice, in which rice grains were painted red, blue, yellow, black or purple in order to leave coded messages or trails.
If you were to lay out all the blood vessels in the human body end to end, they would stretch over 60,000 miles. That's enough to circle the Earth more than twice!
Curly hair may have offered evolutionary advantages
Studies suggest curly hair could have aided heat regulation and brain protection in early humans by trapping air and shielding the scalp from UV radiation more effectively than straight hair.
