"The National Center for Biotechnology Information (NCBI), a division of the National Library of Medicine (NLM) at the U.S. National Institutes of Health, is a leader in the field of bioinformatics; it studies computational approaches to fundamental questions in biology and provides online delivery of biomedical information and bioinformatics tools. NCBI hosts approximately 40 online literature and molecular biology databases—including PubMed, PubMed Central, and GenBank—that serve millions of users around the world. The second edition of the NCBI Handbook, released in November 2013 in conjunction with the 25th anniversary of NCBI, aims to provide a comprehensive overview of the breadth of informatics resources at NCBI, and an in-depth account of the scope, data, infrastructure, processing, and access for each major database or resource. The databases and resources are organized here into seven concept areas: literature, genomes, variation, health, genes and gene expression, nucleotide, proteins, and small molecules and biological assays. Three additional categories encompass tools, infrastructure, and metadata. Each concept area begins with an overview chapter that provides a contextual framework for the resources discussed under that concept; the overview is followed by separate chapters that cover individual databases or resources.

"As with the first edition, The NCBI Handbook 2nd Edition is geared towards advanced users of NCBI resources to provide an understanding of how bioinformatics resources at NCBI work. It is not a step-by-step user manual but complements NCBI user guides, tutorials, help information, and other existing documentation. It is our intent that the handbook will reflect, to the extent possible, the current state of databases, resources, and tools at NCBI, with information updated periodically."