This 2-part series on "Regenerative Medicine" shows how it's possible to replace lost or damaged body parts by using human cells. Cell sheets can be used to restore damaged organs, making them functional again. For instance, they can be transplanted to a patient's cloudy cornea to help restore eyesight. Japanese researchers have also developed new technology to regenerate injured knee cartilage using cell sheets. We share some tips on how to relax our eyes to prevent them from aging prematurely.