IN this issue of GENETICS we launch FlyBook, which will present the current state of knowledge of the molecular biology, cellular biology, developmental biology, and genetics of the fruit flyDrosophila.That we commence this project at the end of the journal’s first century is fitting: it was work on Drosophila that established the genetic basis of Mendel’s laws of inheritance (leading to Drosophila’s first Nobel prize in 1933). In fact, the very first article published in the journal described experiments with Drosophila that established chromosomes as the carriers of hereditary information (watch for a Perspectives article in January commemorating that article).The prominence of Drosophila in the pantheon of “model organisms” is undisputed. T. H. Morgan knew that it could serve as a model multicellular organism when he chose it for his path-breaking work early in the last century, and his prescience has been apparent in nearly every issue of GENETICS. In fact, >20% of the ∼18,000 articles in GENETICS feature “Drosophila” in the title!We did not need to be reminded of how similar Drosophila’s genes are to those of other organisms (including ours) when complete genome sequences started appearing 15 years ago, but it was heartening to see. Studies of Drosophila will no doubt continue to inform biology for decades to come.We have acquired an enormous amount of information about the biology of the fruit fly, and have devised innovative experimental approaches for its study. FlyBook aims to make that information and insight accessible to scientists unfamiliar with Drosophila as well as to the seasoned Drosophila researcher.FlyBook will span the breadth of Drosophila biology in ∼50 chapters that will appear as review articles in GENETICS, and will also be compiled on a separate FlyBook website. This enables FlyBook to benefit from the established infrastructure of GENETICS—its professional preparation and presentation of articles; its indexing, search, and navigation functions; helpful article features unique to GENETICS, such as direct linking of terms to FlyBase; and its outstanding peer editing. GENETICS is a fitting venue for this updated model of a book.Experts in their fields will write the chapters, which will be edited by a stellar group of scientists serving on the FlyBook Editorial Board. We thank our Section editors and the authors for their selfless service to GENETICS, to the Genetics Society of America (GSA), and to science.Work on the fruit fly has yielded much insight into neurobiology, so it is fitting that we launch FlyBook with two articles on this subject. In addition, a Commentary by Gerry Rubin sets FlyBook in perspective.FlyBook continues the GSA’s long tradition of supporting, promoting, and presenting model organism research. FlyBook joins Yeastbook (http://www.genetics.org/content/yeastbook) as an important resource for the genetics community. We are proud to present in this issue of GENETICS the first two chapters of what we know will be a seminal series of articles.