Nanocrystals have emerged as one of the most versatile and clinically relevant platforms for the delivery of poorly soluble drugs, with several nanocrystal-based products already on the market. Produced through both "bottom-up" and "top-down" approaches, drug nanocrystals possess a large specific surface area that enhances the dissolution and absorption of hydrophobic actives, offering a powerful strategy to improve drug performance. This book presents the fundamental principles of nanocrystal technology alongside their broad applications in modern drug delivery. Chapters explore oral bioavailability enhancement, long-acting injectable therapies, topical and transdermal delivery (including microneedles), ocular and mucosal administration, pulmonary delivery, and strategies for targeting the central nervous system. Each contribution highlights both the opportunities and the challenges of applying nanocrystal formulations across therapeutic areas. Intended for drug delivery scientists in both academia and industry, this volume provides a comprehensive overview of nanocrystal research, development, and translation into innovative therapeutic solutions. By combining rigorous science with insights into clinical and commercial impact, it serves as a valuable resource for researchers, students, and professionals aiming to harness nanocrystals in addressing complex therapeutic needs.