And the final phase is called the luteal phase. This is the process by which inside the ovary we form that corpus luteum that acts as a gland during the menstrual cycle, as we'll see in just a moment. Now, menstruation actually takes place at the beginning of the follicular phase and at the end of our luteal phase. So let's take a look at the following diagrams that describe the menstrual cycle. And then let's describe the different steps of the menstrual cycle. So if we examine the diagram, notice the X axis describes our progression of days.