The book is written and edited by an individual fortunate to see and work through the evolution of precision medicine in the last three decades. The book begins with an introduction to genomics and precision medicine, followed by a chapter on pediatric genomic sequencing and nine chapters focused on the pathologic diagnosis required for precision therapies in cancer. Tumors of the central nervous system (the brain and spinal cord) and the thyroid and salivary glands are described, including the most up-to-date World Health Organization (WHO) diagnostic pathologic classifications. The importance of the WHO classification of cancer in precision medicine is discussed. For hematolymphoid neoplasms, a detailed historical background for leukemia and lymphoma classifications precedes the comparison of the 5th edition WHO 2022 classification with the International Consensus Classification. Novel techniques in flow cytometry and measurable residual disease detection in hematolymphoid neoplasms by flow cytometry are described with ample illustrations. Other chapters include liquid biopsies in blood cancer, precision diagnosis in the lung, colorectal, ovarian, and prostate cancers, novel immunotherapies in cancer, including essential concepts underlying pathologic testing in cancer, and digital pathology and artificial intelligence as necessary tools for advancing precision medicine.