Criminalistics covers a diverse set of scientific approaches to and procedures of analyzing physical evidence from a crime scene. Such approaches and procedures include the analysis of hair and fibers, paint, glass, bodily fluids, botanicals and soil, weapons, fingerprints and footprints – and much more. In fact the vast majority of forensic services fall in the realm of criminalistics, which makes this term quite convoluted for laypersons. Trained experts in these methods, called criminalists, may operate at an active crime scene, in a crime laboratory, or both; however, the professionalization of the field is driving practitioners to specialize in smaller segments of criminalistics so as to best serve the needs of modern forensic units. Accordingly, this entry provides a practical introduction to modern criminalistics.