2015). It gives a survey of themes that have been developed during the 100 years of development of general relativity theory.This chapter aims to provide a broad historical overview of the major developments in General Relativity Theory ('GR') after the theory had been developed in its final form. It will not relate the well-documented story of the discovery of the theory by Albert Einstein, but rather will consider the spectacular growth of the subject as it developed into a mainstream branch of physics, high energy astrophysics, and cosmology. Literally hundreds of exact solutions of the full non-linear field equations are now known, despite their complexity [1]. The most important ones are the Schwarzschild and Kerr solutions, determining the geometry of the solar system and of black holes (Section 2), and the Friedmann-Lemaître-Robertson-Walker solutions, which are basic to cosmology (Section 4). Perturbations of these solutions make them the key to astrophysical applications.Rather than tracing a historical story, this chapter is structured in terms of key themes in the study and application of GR:1. The study of dynamic geometry (Section 1) through development of various technical tools, in particular the introduction of global methods, resulting in global existence and uniqueness theorems and singularity theorems.2. The study of the vacuum Schwarzschild solution and its application to the Solar system (Section 2), giving very accurate tests of general relativity, and underlying the crucial role of GR in the accuracy of useful GPSindexGPS systems.3. The understanding of gravitational collapse and the nature of Black Holes (Section 3), with major applications in astrophysics, in particular as regards quasi-stellar objects and active galactic nuclei.4. The development of cosmological models (Section 4), providing the basis for our understandings of both the origin and evolution of the universe as a whole, and of structure formation within it;5. The study of gravitational lensing and its astronomical applications, including detection of dark matter (Section 5).6. Theoretical studies of gravitational waves, in particular resulting in major developments in numerical relativity (Section 6), and with development of gravitational wave observatories that have the potential to become an essential tool in precision cosmology. This Chapter will not discuss quantum gravity, covered in Part Four. It is of course impossible to refer to all relevant literature. I have attempted to give the reader a judicious mix of path-breaking original research articles, and good review articles. Ferreira has recently discussed the historical development at greater length [2].