The discovery of DNA in 1869 changed the world forever. Each subsequent discovery--such as DNA's double helix structure and the nucleotides it contains--dramatically increased humanity's understanding of our own bodies. Of course, the invention of the microscope was crucial to these discoveries. As technology advances and scientists develop more powerful instruments, their knowledge of DNA also increases. Age-accessible main text, augmented with vibrant full-color photographs and informative graphic organizers, introduce young readers to this important scientific topic, making them more informed about their health and laying the foundation for future careers in science and medicine.