A lymph node is divided into compartments called "nodules" (or lobules), each consisting of a region of cortex with combined follicle B cells, a paracortex of T cells, and a part of the nodule in the medulla. The substance of a lymph node is divided into the outer "cortex" and the inner "medulla". The cortex of a lymph node is the outer portion of the node, underneath the capsule and the subcapsular sinus. It has an outer part and a deeper part known as the "paracortex". The outer cortex consists of groups of mainly inactivated B cells called follicles. When activated, these may develop into what is called a germinal centre. The deeper paracortex mainly consists of the T cells. Here the T-cells mainly interact with dendritic cells, and the reticular network is dense.