Students learn about various crystals, such as kidney stones, within the human body. They also learn about how crystals grow and ways to inhibit their growth. They also learn how researchers such as chemical engineers design drugs with the intent to inhibit crystal growth for medical treatment purposes and the factors they face when attempting to implement their designs. A day before presenting this lesson to students, conduct the associated activity, Rock Candy Your Body.

This lesson helps students explore the functions of the kidney and its place in the urinary system. Students learn how engineers design instruments to help people when kidneys are not functioning properly or when environmental conditions change, such as kidney function in space.

In this activity, students filter different substances through a plastic window screen, different sized hardware cloth and poultry netting. Their model shows how the thickness of a filter in the kidney is imperative in deciding what will be filtered out and what will stay within the blood stream.

Students learn how crystallization and inhibition occur by examining calcium oxalate crystals with and without inhibitors that are capable of altering crystallization. Kidney stones are composed of calcium oxalate crystals, and engineers and doctors experiment with these crystals to determine how growth is affected when a potential drug is introduced. Students play the role of engineers by trying to determine which inhibitor would be the best for blocking crystallization.