Origami is a traditional Japanese art of paper folding that started in China in the 2nd century AD and was popularized outside of Japan in the mid-1900s. It involves folding sheets of paper into shapes and figures without cutting or gluing, with the earliest origami in Japan dating back to the 6th century when it was used for religious ceremonies. The first known origami book published in Japan was in 1797 called "How to Fold 1000 Cranes".