The Mystery of Tears

Why do we feel better after a good weep? What makes us cry for joy, or grief, or triumph? What use are tears? If we knew why we cry, perhaps we could find new ways to treat dry-eye disease or handle stress. Dr Bill Frey is looking for the causes of crying at his Dry Eye and Tear Research Centre in Minnesota. But before he starts work, he faces a major problem - how can he get people to weep when he wants?