Henna is a form of art which involves decorating hands and feet with designs made out of leaves from henna plant. Following are the pictures of a henna plant.
The traditional process is to grind these henna leaves and make a paste out of it. And apply the paste in several designs. The leaves have several medicinal elements. First and primary being the instant cooling effect when applied to the body especially palms and feet. It is known to remove several skin/foot diseases.
The rich color of stain that henna leaves on the skin on contact is very appealing and attractive.
Since it is not possible to get the fresh leaves everytime, an alternative to have access to henna is to dry the leaves, and make a powder from it.
The powder can be mixed with water or lemon juice or tamarind juice and the resultant paste is coned in much like cones for cake icing. These cones are then very convenient to draw simple or intricate henna designs. Henna is totally organic, biodegradable and excitingly green way to adorn the palms and feet.
For more details to the history of Henna in human civilization, you can read more at:
http://silknstone.com/About-Henna.html
http://en.wikipedia.org/wiki/Henna