This introductory chapter provides background to motivate the study of biological materials with nanoindentation techniques. The reasoning behind investigations of the mechanical behavior of biological materials is introduced, as are the particular reasons for conducting these investigations at small physical length-scales. A taxonomy for biological materials is presented, emphasizing a top-down hierarchical system for classification, from organs to tissues and down in scale, including the molecular building blocks for both cells and extracellular matrix material. Typical implementation of nanoindentation testing is described and limitations in applying the technique to biological systems are presented. This overview motivates the content contained in the remainder of this volume, including investigation of fundamental contact mechanics principles appropriate to biological systems and application of nanoindentation techniques to the characterization of biological materials.