Why learn from drawings in a book when you can learn from the structures themselves? Over 40,000 structures of DNA, RNA, and proteins are stored in public databases. Using free software from the National Library of Medicine, you see DNA and proteins come to life in three-dimensions! Written for a general audience, A Beginner's Guide to Molecular Structures is designed to help anyone learn how to find and manipulate molecular structures using the free-viewing program, Cn3D. Working with structures is fun, Cn3D is easy to use, and it works on both Windows and Mac OS X.