Part I Basic Concepts.- 1 Introduction.- 2 Polarized Light.- 3 Polarized Electrons.- 4 Experimental Geometries and Approaches.- 5 Density Matrices: Connecting Experiment and Theory.- 6 Computational Methods.- Part II Case Studies.- 7 Electron Impact Excitation.- 8 Ion and Atom Impact Excitation.- 9 Propensity Rules.- 10 Impact Ionization.- 11 Photo-Driven Processes.- 12 Related Topics and Applications.- Part III Selection of Historical Papers (1925-1976).-...