Knowledge of root and root canal morphology is a prerequisite for effective non-surgical and surgical endodontic treatments. The external and internal morphological features of roots are variable and complex, and several classifications have been proposed to define the various types of canal configurations that occur commonly. Thorough knowledge of tooth morphology, careful interpretation of angled radiographs, proper access preparation, and a detailed exploration of the interior of the tooth are essential for a successful treatment outcome. An understanding of the complexity of the root canal system is essential for understanding the principles and problems of shaping and cleaning, for determining the apical limits and dimensions of canal preparations, and for performing successful microsurgical procedures.