Precision medicine requires precision drugs that match the needs of individual patients. An ideal drug, popularly referred to as the "magic bullet", should be effective without causing any unwanted side effects. To do this, drugs must act solely on the target of the disease. Despite major efforts in this area over some 50 years, the currently available drugs are far from being "idea". This book summarizes the key requirements for developing precision drugs and offers a new paradigm for site-specific drug delivery. As such, it will be of interest to personnel involved in drug development at pharmaceutical and biotech companies and academic institutions.