Book excerpt: The leaf surface or phyllosphere is a major habitat for microorganisms. Microbes on or within leaves play important roles in plant ecology, and these microbes can be manipulated to enhance plant growth or reduce plant disease. This book presents a number of critical reviews by internationally recognized experts on the microbial ecology of leaves. Topics include methods of assessment of microbial populations on leaf surfaces, leaves as reservoirs of ice nucleation phenomenon, and leaves as microbial habitats in both aquatic and terrestrial environments. The book will be of interest to students and scientists in numerous disciplines, including botany, aerobiology, meteorology, ecology, agriculture, and microbiology.