The renin-angiotensin-aldosterone system (RAAS) is a critical regulator of blood volume, electrolyte balance, and systemic vascular resistance. While the baroreceptor reflex responds short term to decreased arterial pressure, the RAAS is responsible for acute and chronic alterations. The classical understanding of RAAS is that it comprises three significant compounds: renin, angiotensin II, and aldosterone. These three compounds elevate arterial pressure in response to decreased renal blood pressure, salt delivery to the distal convoluted tubule, and beta-agonism. The understanding of RAAS has expanded tremendously due to discoveries of newer system components over the last few decades. The discussion in this article will be limited to the components of the classical pathway of the renin-angiotensin-aldosterone system.