Ellipsometry is the method of choice to determine the properties of surfaces and thin films. It provides comprehensive and sensitive characterization in contactless and non-invasive measurements. This book gives a state-of-the-art survey of ellipsometric investigations of organic films and surfaces, from laboratory to synchrotron applications, with a special focus on in-situ use in processing environments and at solid-liquid interfaces. In conjunction with the development of functional organic, meta- and hybrid materials for new optical, electronic, sensing and biotechnological devices and fabrication advances, the ellipsometric analysis of their optical and material properties has progressed rapidly in the recent years.