9.1. Introduction 9.1.1. Bulk magnetism in retrospect 9.1.2. Surface magnetism: A new interdisciplinary research discipline 9.2. Basic concepts in the magnetism of surfaces and thin film systems 9.2.1. The ground state electronic structure (T = 0K) 9.2.1.1. A bulk ferromagnet 9.2.1.2. A semi-infinite magnetic crystal 9.2.1.3. Ultrathin films: 2-dimensional entities 9.2.2. Magnetism at T > 0K 9.2.2.1. Magnetic excitations in the bulk 9.2.2.2. Surfaces and thin films 9.2.3. Magnetic anisotropies 9.2.3.1. The bulk 9.2.3.2. Surfaces and thin films 9.3. Probing surface magnetism with spin-polarized electrons 9.3.1. Description of polarized electrons 9.3.2. Polarized electron sources 9.3.3. Spin polarimeters 9.4. Scattering of spin-polarized electrons from magnetic surfaces 9.4.1. Elastic scattering (SPLEED) 9.4.1.1. Magnetic structure analysis 9.4.1.2. Temperature dependence of the surface magnetization in the spin-wave regime 9.4.1.3. Critical phenomena at surfaces 9.4.1.4. Magnetic size effects in ultrathin films 9.4.1.5. Interlayer coupling in magnetic trilayers 9.4.2. Inelastic scattering (SPEELS) 9.4.2.1. Stoner excitations at magnetic surfaces 9.4.2.2. Stoner excitations in ultrathin films 9.4.2.3. Stoner excitations and magnetic ordering 9.5. Emission of spin-polarized electrons from ferromagnets