Hydrogen, the first and most abundant element in our universe, is an essential zero-carbon fuel in humanity''s race against catastrophic climate change. However, very few have access to cryogenic hydrogen systems to gain the necessary experience to contribute. This textbook is written as an invitation for scientists and engineers with experience in thermodynamics, fluid mechanics, and heat transfer to engage in this race for the future via cryogenic hydrogen research and development. It begins with the history of hydrogen and cryogenics to create a context for current needs. Next, the text builds a foundation for hydrogen''s unique quantum mechanical effects on bulk thermophysical properties, and how to choose from and utilize available property models. Practical methods are presented for sensing and conversion between the quantum mechanical forms.Foundational aspects of hydrogen liquefaction and cooling in recuperative and regenerative cycles are presented next. Elements of hydrogen t
