Objectives clearly identify the knowledge and skills to be obtained when the chapter is completed. Guided Tour Illustrations have been designed to clearly and simply communicate the specific topic. Illustrations have been completely replaced and updated for this edition. Photographic images have been updated to show the latest equipment. Scientist Profiles provide you with brief biographical information on a scientist discussed in the chapter. Technical Terms list the key terms to be learned in the chapter. Safety Notes alert you to potentially dangerous materials and practices.