Frontiers of Science Online (FoSO) is a free resource for college science teachers who seek to access and share materials and approaches to undergraduate science instruction. The e-textbook, lectures, media, activities, problem sets, seminar guides, and other exemplary teaching materials on this site were generated for use in Columbia University's innovative core course, Frontiers of Science. On FoSO you can browse and search for teaching resources, store favorite resources in your own FoSO Library, hold online discussions with your colleagues at other institutions, and much more.