Button Mushrooms are small to medium in size with caps averaging 2-7 centimetres in diameter and are attached to short, truncated stems. The smooth white caps are rounded, firm, and spongy. When bruised, the white flesh will turn light pink and will then transform into brown. Mushrooms are 90% water and virtually calorie-free. They are also rich in potassium, selenium, protein, and cancer-preventing antioxidants often used as a raw topping on salads and dips.