The field of molecular imaging of living subjects has evolved considerably and has seen spectacular advances in engineering, chemistry and biomedical applications. This downloadable textbook, Molecular Imaging: Principles and Practice (PDF) by Ralph Weissleder and others, was designed to fill the need for an authoritative source for this multi-disciplinary field. We have been fortunate to recruit over eighty leading authors contributing 75 individual chapters. Given the multidisciplinary nature of the field, the ebook is broken into 6 Molecular Imaging in Cell and Molecular Biology,different sections: Molecular Imaging technologies, Applications of Molecular Imaging, Molecular Imaging in Cell and Molecular Biology, Chemistry, Molecular Imaging in Drug Evaluation with the final section comprised of chapters on bioinformatics, computation and modeling. The organization of this large amount of information is logical and strives to avoid redundancies among chapters. It encourages the use of figures to illustrate concepts and to provide numerous awesome molecular imaging examples.