For a class of 30 working in pairs. Students build a simple model of the renal artery, renal vein, glomerulus, and nephron to simulate kidney filtration and learn about the process of excretion. Using beads of different sizes and colors to represent essential blood components, they model the filtration process that occurs in the kidney as blood flows in via the renal artery. Students also learn about the process of complete and selective reabsorption and explore why urinalysis is such a powerful tool in diagnosing disease.