What’s little and sticky and turns 20 today? The Post-It. 3M corporate scientist Art Fry, now 68, tired of using paper clips and slips of paper to keep his place in his church hymnal. His solution? He and a fellow scientist married a new adhesive to square yellow slips of paper. “My biggest reward,” Fry says today, “is to see so many people use and appreciate my product.” Could you flag that for us, Art?