Like the lymph node, the human spleen is a highly compartimentalized organ. Each compartment has its own structure, cell population, and functions. These include the white pulp with T-cell areas and B-follicles, the non-filtering lymphoid areas of the red pulp, the border between red and white pulp (the perifollicular zone), the red pulp cord tissue and sinuses, and the perivascular rim. These structures are described and illustrated. In addition, we indicate how they relate to pathological alterations.