Renal clearance, the volume of blood cleared of a substance in a particular time period, is commonly recognized as one of the most difficult concepts in physiology. This difficulty may in part reflect the quantitative nature of renal clearance since many life sciences majors perceive that mathematics is irrelevant to their discipline. Students may infer from the clearance definition that, in blood leaving the kidney, the blood volume corresponding to the clearance will be completely free of the substance, but the remainder of the blood volume will contain the original concentration. Thus, renal clearance is difficult for students to master both qualitatively and quantitatively. A variety of excellent case studies have been developed to address the quantitative aspect; these provide opportunities to practice calculating clearance and other indicators of renal handling (3, 4, 6). However, although students may become proficient at slotting clinical values into memorized formulae, personal experience suggests that these activities do not always result in conceptual understanding, even when coupled with well-designed diagrams and videos. Using clay droplets to represent water volumes (50 ml/droplet) and beads to represent solutes (10 mg/bead), students trace the path of solutes and water as they enter the glomerulus, are exchanged between the tubule and peritubular capillaries, and eventually leave the kidney in urine or in the renal vein. The simulation thus allows students to visualize and enact dynamic processes in a way that cannot be done with data sets, images, or videos. This activity was developed to improve student understanding by modeling the renal handling of different solutes in a quantifiable manner.