This book describes the development of portable, wearable, and highly customizable hand exoskeletons to aid patients suffering from hand disabilities. It presents an original approach for the design of human hand motion assistance devices that relies on (i) an optimization-based kinematic scaling procedure, which guarantees a significant adaptability to the user hands motion, and (ii) a topology optimization-based design methodology, which allowed the design of a lightweight, comfortable device with a high level of performance. The book covers the whole process of hand exoskeleton development, from establishing a new design strategy, to the construction and testing of hand exoskeleton prototypes, using additive manufacturing techniques. As such, it offers timely information to both researchers and engineers developing human motion assistance systems, especially wearable ones.