What is a henna tattoo?

It's a temporary tattoo that is created by using Henna which is a dye. I am not sure what it's made from but I know that East Indians use it in ceremony.

And most importantly Henna tats are needleless

Henna is made from a henna plant there is red which shows on the skin as red or orange and black which shows on the skin as black purple and sometimes blue it is indeed needless and it can also be used to dye hair i myself used to dye my hair with red henna you can purchase the DIY henna from Micheal's craft stores for henna tattoo and for henna dye you can purchase from middle-eastern stores i must advise it as a bit of a smell...