We know that genetics determines a lot about the people we become. DNA informs why our eyes are blue and our sense of humor is too. Biological inheritance is why your kid reminds you of your parents. Still, understanding the actual dynamics at play can be extremely difficult. While eye color is a relatively easy (remember that recessive genes lesson you got in middle school?), figuring out the source of genetic diseases and behavior is extremely complicated. Genetic tests can help, but it doesn’t make anything simple.

That’s why Fatherly dove into the science of genetics with this guide. So you can better understand your own DNA as well as your kid’s, we talked to scientists about hair loss, mutations, CRISPR, and even penis size. While researchers are making new genetic breakthroughs every day, here’s what we know about DNA and how it’s shaping your family.