S1, E3: They are potent symbols of sex, fertility, and nurturing. They are also changing. Human breasts are growing bigger and appearing earlier, with higher rates of cancer than ever before. Why? Is it a product of evolution? Obesity? The chemicals around us? Follow doctors and scientists, who are using new ways of analyzing breast tissue, and revealing startling and disturbing truths. Then witness the surprising discoveries made when modern science puts breast tissue and breast milk under the microscope.