Book excerpt: Physical Methods, Instruments and Measurements theme is a component of the Encyclopedia of Physical Sciences, Engineering and Technology Resources which is part of the global Encyclopedia of Life Support Systems (EOLSS), an integrated compendium of twenty Encyclopedias. The Theme provides a complete survey of the present status of our knowledge of modern physical instruments and measurements. It is organized in the following main topics: Measurements and Measurement Standards; Sources of Particles and Radiation, Detectors and Sensors; Imaging and Characterizing – Trace Element Analysis; Technology of Physical Experiments; Applications of Measurements and Instrumentation which are then expanded into multiple subtopics, each as a chapter. These four volumes are aimed at the following five major target audiences: University and College Students, Educators, Professional Practitioners, Research Personnel and Policy Analysts, Managers, and Decision Makers and NGOs.