One aim of developmental biology is to learn how a healthy body arises from the genetic material of an organism, also known as a genome. Another goal is to understand why development sometimes goes wrong. Mutations may produce organisms with harmless--or potentially beneficial--characteristics such as extra fingers. Other times they can lead to fatal developmental defects, or problems that make it impossible for someone to lead a healthy life. They are also the reason that new species can arise. Over the past few years, research has drawn together development, medicine, and several other branches of biology in a new way of thinking about organisms that many people are still not familiar with.