Conventional root canal therapy is extensively used for treatment of irreversible pulpitis and periapical periodontitis today. However, the treated teeth with obturation by Gutta Percha and sealer are susceptible to fracture and re-infection. Regeneration of loss tissue of pulp/dentin complex or keep the remained vital tissue to maintain the tooth viability is of great interest. Currently, some cases such as immature young permanent teeth (incisors, premolars and molars) are successfully revascularized with root elongation, canal wall thickness, apical lesion healing, and most surprisingly pulp vitality recovery. Some clinical cases in adult teeth have been successfully revascularized in our clinic. Furthermore, vital pulp tissue in some specific teeth with irreversible pulpitis or apical radiolucency can be maintained. The topic will present protocols for various clinical cases, summarize tips for clinical procedures and materials selection. Some recent laboratory studies performed in HKU will also be discussed.