XAS advances and principles with the International Tables for Crystallography, Volume I: The beginning of XAFS and a new ruler

X-ray Absorption Spectroscopy (XAS) and X-ray Absorption Fine Structure (XAFS) are powerful tools to characterise local structural information around an element of many chemically sensitive materials. XAFS has had a long history of exciting successes and advances, and remains a live and developing major field of science, especially for nanostructural determination for many non-ideal and non-crystalline materials. Key issues and topics of discussion and understanding today are summarised by world leaders in the International Tables for Crystallography, Volume I: X-ray Absorption Spectroscopy and Related Techniques. Hence this Handbuch and Encyclopaedia, the first for XAS, encourages a continuing and rich dialogue on current and future developments, advances and principles. As in all science, a new metric, a new paradigm, a new experimental type usually leads to new science and opportunities. In this manuscript, the key basics of XAFS measurement, analysis and theory are introduced with an overview of progress achieved from the history and reflected in the new Volume and lessons remaining to be developed. This work links successes and challenges in XAFS research, to point the reader to best current and future metrics, and to a new ruler for measurement, analysis and theory.