This chapter explains the histological organisation of the protective periodontium, consisting of the gingiva and the dentogingival junction. You will learn that you can distinguish an attached gingiva, attached to the alveolar bone, a free gingiva, not attached to the alveolar bone, and you will see how the mucosa of both gingivae is organised. It is explained that the dentogingival junction is formed by the gingival sulcus, the sulcular epithelium and the junctional epithelium, which are supported by a lamina propria. You will learn the peculiar characteristics of the junctional epithelium. You will also see the structure of the interdental gingiva. The organisation of the gingival ligament is explained. Finally, you will study the origin of the protective periodontium, its innervation and vascularisation.