The Regeneron International Science and Engineering Fair (Regeneron ISEF) is the world's largest international pre-college science competition. Each year, ISEF brings over 1,800 high school students from 75 countries to exhibit and demonstrate ingenuity and innovation through science projects of their own design. Students in grades 9-12 or equivalent must compete in a Regeneron ISEF affiliated science fair and win the right to attend Regeneron ISEF.  Each affiliated fair may send a pre-determined number of projects to ISEF (as calculated by participation and high school population) to compete in 21 different categories.