Biotechnology and molecular techniques pervade all aspects of modern life, both in and out of the laboratory. Techniques that allow researchers to quantify cellular RNA and proteins, amplify DNA, and create recombinant DNA molecules were developed using enzymes isolated from microbes. This chapter discusses many techniques including those that allow scientists to map protein-protein interactions, design novel vaccines, and even carry out evolution in a test tube. Recent advances in gene therapy are explored. The experimental tools presented in this chapter will appear throughout your text and are fundamental to understanding current biology research. Biotechnology, the use of organisms and their products to improve human and environmental welfare, is a growing field and will only continue to gain in importance. Knowledge of this field will not only make you a better scientist, it will make you a more informed citizen.