Meet Louis von Ahn, computer scientist and professor at Carnegie Mellon who is already at the top of his field at age 30!  In this video for grades 6-12 from NOVA scienceNOW, students can learn about one of his most successful ideas—CAPTCHA—a test that humans can pass but computers cannot, which has been used to improve the security of Internet sites.  They’ll also discover how he comes up with his innovative ideas, and how CAPTCHAs have been reinvented to help digitize old books.  Resources include background essay, discussion questions and National Standards/Benchmarks for Science Literacy.