A new generation of large, ground-based telescopes are just coming into operation. They will take astronomical research well into the next century. These extremely powerful telescopes demand specially designed instruments and observing techniques. The VII Canary Islands Winter School of Astrophysics gathered together leading experts from around the world to review this technology. Based on the meeting, this timely volume presents eight specially written chapters covering all aspects of telescope instrumentation. This book provides an essential reference for all astronomers who will be the users of these large telescopes. It reviews both the challenges involved in designing successful instrumentation and the questions in astronomy they must address. We are taken from the fundamentals of astronomical imaging, low- and high-resolution spectroscopy, and polarimetry up to the state-of-the-art technology in adaptive optics and laser guide stars, interferometry, image pattern recognition, and optical, near and mid infrared arrays. This timely volume provides an excellent introduction for graduate students and an invaluable reference for researchers using the latest generation of large astronomical telescopes.