"Version: 202112"--Title page verso.Includes bibliographical references.1. Introduction -- 1.1. Earlier classifications -- 1.2. Hubble's tuning fork -- 1.3. The 90% rule -- 1.4. Assignments -- 1.5. Further reading2. Galaxy scale -- 2.1. Introduction -- 2.2. de Vaucouleurs profile -- 2.3. Exponential profile -- 2.4. S?ersic profile -- 2.5. Two-component galaxies -- 2.6. Vertical profiles -- 2.7.…