 DNA is the code of instructions that makes you, you. The human body has about 50 trillion cells, and each cell contains the same exact copy of your DNA. If all the DNA in your body was lined up end-to-end, it would stretch from Earth to Jupiter 100 times over. By 2003, the arduous task of writing down all the letters in the human genome was completed, three billion pairs of chemicals known by the letters A, C, T, and G. To me, the genome is three billion separate stories. Every letter in the human genome has a story. Sometimes it's a story about history, sometimes it's a story about medicine, sometimes it's a story about deep evolution. It's an amazing set of stories, and so no one story is what excites me about the human genome. It's realizing you have in front of you a book of three billion stories. Each of us has this book, and we share about 99.9% of the exact same letters. But it's that tiny bit of difference that makes our individual biographies so compelling. For me, one of the exciting results is that it breaks down any traditional notions of race. There aren't three, five, ten human races, but rather there's this beautiful continuum. It turns out characteristics we thought were genetically straightforward are not. For example, the genetic code for blonde hair in the Solomon Islands is different from the code for blonde hair in California. And there's more variation on average between the genomes of two people from different regions of Africa than between an African and a European. The way our DNA works is a constant revelation. Scientists used to think that as much as 97% of our genome served no direct purpose in how our bodies functioned, it was dismissed as junk. You didn't need them. It wasn't obvious what they did. They weren't coding for proteins. It must be junk. Turns out that a lot of it's not junk. And a lot of it plays a very important role in choreographing what our genes do. Another huge surprise was the total number of genes encoded by our DNA. Because human beings are such a complex species, scientists initially thought we might have as many as 100,000 genes. It turns out we only have about 20,000. Compare that to rice with upwards of 50,000. Every day, scientists around the world are discovering new ways to make sense of the DNA book of life. It's a journey that has just begun. I often will say that truly interpreting the human genome sequence will take many decades to fully accomplish. I'm convinced my children will be interpreting the human genome sequence. My children's children and maybe even generations beyond that.