1-Naphthylacetic acid (NAA) is a synthetic plant hormone belonging to the auxin family. It is commonly used in horticulture and agriculture to promote root formation and growth in plant cuttings and tissue culture. NAA is also utilized in fruit thinning, flower induction, and fruit development in various crops. It functions similarly to natural auxins, stimulating cell elongation and division, and is available in various formulations for different applications.