The primary concern of the clinician is the 3-dimensional cleansing of the root canal system. The length of the root canal is a dimension which has been studied since long. But advancements in the imaging techniques and growing research has shown that the apical third of the root canal system has varying shapes that can lead to difficulties in the efficient cleaning & complete elimination of bacteria and debris. This article attempts to review various aspects related to the apical third dimension, techniques & methods presently available for its gauging, factors affecting the measurement and instruments or systems which claim a 3-dimensional cleaning and shaping of the apical third.