A lot of people have tattoos: an estimated 12% of Europeans and 24% of Americans. What’s in tattoo ink, and how are different coloured tattoos produced? This graphic for National Tattoo Day (July 17) takes a look.
The Muslim festival of Eid al-Adha started on Sunday evening and runs through until Thursday. As part of the celebrations, some create impressively intricate art on their hands using henna. Here we take a look at the molecules in henna that allow it to be used as a dye, and how this process works.