One of a series of general interest publications on science topics, the booklet provides those interested in the study of caves (speleology) with a nontechnical introduction to the subject. Separate sections examine types of caves, how caves form, cave features, minerals found in caves, uses of caves, and caves as natural underground laboratories. The final sections present a brief description about caves to explore in the United States (with a map showing locations of known caves) and precautions to take when exploring newly discovered or unattended caves. (LH)