This book reports on cutting-edge research into innovative system interfaces, highlighting both lifecycle development and human-technology interaction, especially in virtual, augmented and mixed-reality systems. It describes advanced methodologies and tools for evaluating and improving interface usability and discusses new models, as well as case studies and good practices. The book addresses the human, hardware, and software factors in the process of developing interfaces for optimizing total system performance, while minimizing their costs. It also highlights the forces currently shaping the nature of computing and systems, such as: the importance of portability and technologies for reducing power requirements; the necessity of a better assimilation of computation in the environment; as well as solutions to promote accessibility to computers and systems for people with special needs. The book, which is based on the AHFE 2019 International Conference on Human Factors and Systems Interaction, held on July 24-28, 2019, in Washington D.C., USA, offers a timely survey and practice-oriented guide for systems interface users and developers alike.