If We All Share 99.9% of DNA, How Can It Still Tell Us Apart?

If humans are 99.9% genetically identical, how can DNA testing reveal who our relatives are—or even who we are? In this video, we explore the fascinating science that makes it possible to trace family lines, distinguish individuals, and unlock hidden ancestry using just a fraction of our genetic code. The answer lies in that 0.1%—and it’s more powerful than you think.