Let's make this birthday one to remember.

83 years old (Born on March 29, 1942)

Happy Birthday, Ann Kiessling! May your day be filled with more excitement than discovering reverse transcriptase activity in normal human cells—though let's face it, that's a tough one to beat. Your groundbreaking work has truly rewritten biology textbooks and inspired countless scientists (and probably confused a few undergrads along the way).

From pioneering America's first human egg donor program for stem cell research back in 2000 to continually pushing boundaries today, you've shown us all that innovation never gets old—even if birthdays do. Here's hoping this year brings you as much joy and success as your remarkable career has brought the scientific community!