Although people can look quite different from one another, all of us share 99.9% of the same DNA. So what makes us individuals? Our inherited differences—from our eye color to our risk for certain diseases-stem from the one tenth of one percent of human DNA that varies from person to person. Because our DNA contains more than three billion bits of information, this tiny percentage amounts to more than three million differences. Additionally, much of our individuality is not controlled by our genes, and instead develops from environmental, social and cultural influences, as well as from human behavior and thought.