An up-to-date survey of the current exciting state of telomere biology. Telomeres--specialized structures found at the ends of chromosomes--are essential for maintaining the integrity of chromosomes and their faithful duplication during cell division. Chapters in this volume cover telomere structure and function in a range of organisms, focusing on how they are maintained, their roles in cell division and gene expression, and how deficiencies in these structures contribute to cancers and other diseases and even aging.