Pharmacology is a branch of medicine which is associated with the study of drug action. A drug can be characterized as any man-made, natural, or endogenous molecule. These drugs can have a biochemical or physiological effect over the cell, tissue, organ, or organism. In vivo imaging or preclinical imaging refers to the visualization of living animals for research purposes, such as drug development and cancer research. Imaging modalities are used in identifying changes, either at the organ, tissue, cell, or molecular level. The imaging systems can be characterized into morphological/anatomical and molecular imaging techniques. The aim of this book is to present researches that have transformed this discipline and aided its advancement. It contains some path-breaking studies in the field of pharmacology and in vivo imaging. The book is appropriate for students seeking detailed information in this area as well as for the experts.