This is a design of henna that an art teacher did freehand for me while I was in Egypt
Henna has been used for body art and hair dye since the Bronze Age, henna has had a recent renaissance in body art due to improvements in cultivation, processing, and the diasporas of people from traditional henna using regions.
The word "henna" comes from the Arabic name for Lawsonia inermis, pronounced /ħinnaːʔ/ or colloquially /ħinna/.
In the Bible's Song of Songs and Song of Solomon, henna is referred to as Camphire.
Henna body art is made by applying henna paste to the skin: the lawsone in the paste migrates into the outermost layer of the skin and makes a red-brown stain.
Whole, unbroken henna leaves will not stain the skin. Henna will not stain skin until the lawsone molecules are made available (released) from the henna leaf. Fresh henna leaves will stain the skin if they are smashed with a mildly acidic liquid. This will stain skin within moments, but it is difficult to form intricate patterns from coarse crushed leaves. Dried ground, sifted henna leaves are easily worked into a paste that can be used to make intricate body art. Commercially available henna powder is made by drying the henna leaves and milling them to powder, then the powder is sifted. This powder is mixed with lemon juice, strong tea, or other mildly acidic liquids
Once applied to the skin, lawsone molecules gradually migrate from the henna paste into the outer layer of the skin. Though henna's lawsone will stain the skin within minutes, the longer the paste is left on the skin, the more lawsone will migrate. Henna paste will yield as much dye as the skin can easily absorb in less than eight hours. Henna tends to crack and fall off the skin during these hours, so it is often sealed down by dabbing a sugar/lemon mix over the dried paste, or simply adding some form of sugar to the paste. This also adds to the colour of the end result, increasing the intensity of the shade.
When the paste has fallen off the skin or been removed by scraping, the stain will be orange, but should darken over the following three days to a reddish brown. Soles and palms have the thickest layer of skin and so take up the most lawsone, and take it to the greatest depth, so that hands and feet will have the darkest and most long-lasting stains. Steaming or warming the henna pattern will darken the stain, either during the time the paste is still on the skin, or after the paste has been removed. Chlorinated water and soaps may spoil the darkening process: alkaline may hasten the darkening process. After the stain reaches its peak color it will appear to fade. The henna stain is not actually fading, the skin is exfoliating: the lower, less stained cells, rise to the surface, until all stained cells are shed.
Henna has been used to adorn young womens bodies as part of social and holiday celebrations since the late Bronze Age in the eastern Mediterranean. The earliest text mentioning henna in the context of marriage and fertility celebrations comes from the Ugaritic legend of Baal and Anath , which has references to women marking themselves with henna in preparation to meet their husbands, and Anath adorning herself with henna to celebrate a victory over the enemies of Baal. Wall paintings excavated at Akrotiri (dating prior to the eruption of Thera in 1680 BCE) show women with markings consistent with henna on their nails, palms and soles, in a tableau consistent with the henna bridal description from Ugarit  Many statuettes of young women dating between 1500 and 500 BCE along the Mediterranean coastline have raised hands with markings consistent with henna. This early connection between young, fertile women and henna seems to be the origin of the Night of the Henna, which is now celebrated world-wide.
The Night of the Henna was celebrated by most groups in the areas where henna grew naturally: Jews, , Muslims, Hindus, Christians and Zoroastrians, among others, all celebrated marriages by adorning the bride, and often the groom, with henna.
Across the henna-growing region, Purim , Eid, Diwali, Karva Chauth, Passover, Nawruwz, Mawlid, and most saints days were celebrated with some henna. Favorite horses, donkeys, and salukis had their hooves, paws, and tails hennaed. Battle victories, births, circumcision, birthdays, Zar, as well as weddings, usually included some henna as part of the celebration. When there was joy, there was henna, as long as henna was available. 
Henna was regarded as having Barakah, blessings, and was applied for luck as well as joy and beauty. Brides typically had the most henna, and the most complex patterns, to support their greatest joy, and wishes for luck. Some bridal traditions were very complex, such as those in Yemen, where the Jewish bridal henna process took four or five days to complete, with multiple applications and resist work.
The fashion of "Bridal Mehndi" in Northern Libya and in North Indian diasporas is currently growing in complexity and elaboration, with new innovations in glitter, gilding, and fine-line work. Recent technological innovations in grinding, sifting, temperature control, and packaging henna, as well as government encouragement for henna cultivation, have improved dye content and artistic potential for henna.
Though traditional henna artists were Nai caste in India, and barbering castes in other countries (lower social classes), talented contemporary henna artists can command high fees for their work. Women in countries where women are discouraged from working outside the home can find socially acceptable, lucrative work doing henna. Morocco, Mauritania, Yemen, Libya, Somalia, Sudan, as well as India and many other countries have thriving womens henna businesses. These businesses are often open all night for Eids, Diwali and Karva Chauth, and many women may work as a team for a large wedding where hundreds of guests will be hennaed as well as the bride and groom.