THE astonishing diversity of life on our planet offers almost unlimited opportunity for experimentation aimed at understanding the principles of the propagation of life. Yet most of what we know about the mechanisms of life has come from studying a select few organisms. The Security Council of the biological nations has revealed the basis of heredity, the mechanisms of expression of genetic information, the principles of organism development, and much more.There are two primary reasons for the success of a research program that focuses on just a few organisms as models for all of life. First, they were wisely chosen for their properties that make them particularly amenable to study: bacteria (and their viruses) and yeasts are easy to grow in large numbers; flies can be easily mated and offer a cornucopia of phenotypes; and the fate of every cell in the worm can be traced from conception to demise. Perhaps more important, focusing on a few species provides for the critical mass of investigators necessary to make true progress. The sharing of resources, methods, and ideas fuels a synergy that propels a field.But our understanding of life would be much less complete without the advances that came from examining organisms not privileged with a place on the Security Council. Studies of frogs and sea urchins revealed fundamental principles of development. Analysis of adenovirus transcripts uncovered introns. Tetrahymena gave us the telomere; squid gave us the action potential. And observations of the progeny of peas revealed the principles of heredity. Clearly, it behooves us to take full advantage of the diversity of life in our quest to understand our world.Remarkable advances in technology, new discoveries, and new experimental tricks have recently brought many more organisms within experimental reach. Fantastic new ways to determine DNA sequence enable anyone to obtain the gene list of virtually any organism, to study the expression of those genes, and to find mutations in them. And RNA interference has provided for many organisms what was once the sole province of a few model organisms: facile inhibition of gene function. The Security Council of organisms is no longer so secure; our experimental reach extends farther and wider than ever before into the larger General Assembly of organisms.This is great news for geneticists because it opens to exploration vast biological frontiers. Exploitation of those frontiers will require guidebooks, and the Editors of GENETICS intend to provide some of them. In this issue, GENETICS launches a new “Toolbox” series of reviews that describes resources—both practical and intellectual—available for the study of less commonly used experimental organisms. Our first Toolbox article describes the experimental tools available for studying the sea squirt, Ciona intestinalis, an increasingly popular organism for developmental biologists. We also have in the pipeline Toolbox articles on Medaka fish and Planaria. We intend this to be a regular series that will expand our experimental horizon. Please send your suggestions for experimental frontiers for which you would like a guidebook.In the meantime, welcome to the expanding world of model organisms!