Henna is a shrub known as Lawsonia Inermis. It holds a red dye that stains or prints on any natural surface it comes in contact with (wood, leather, paper, skin, hair), when appropriately mixed.
Henna has first been used to nourish and dye hair. It is the only 100% natural hair dye. It also works very well as a conditioner. The dyed hair with henna gives a red to brown color tone depending on your original/natural hair color.