Henna, a flower native to Asia and the Mediterranean coast of Africa, is one of the oldest cosmetics still in use. It's been used to transfer patterns onto the skin and as hair dye for centuries, back to the days of Cleopatra and Nefertiti, who were some of the first to make it known for its beauty functions. If you want to try out a little-more-natural hair colour route this fall, give henna a try and keep in mind these best practices.