The active component in jalapenos and other hot peppers is capsaicin, which gives them their strong spicy pungent character.  Tolerance levels in individuals can vary widely—use them in moderation at first.  Eating cold yogurt or drinking milk will help dilute the capsaicin concentration, thereby reducing that “burning” sensation.  Jalapeno peppers are a rich source of vitamin C.  They also contain high levels of vitamins A, E, and K, and the minerals iron and potassium.  Remember to take precautions when preparing hot peppers like jalapenos.  Wear rubber gloves when chopping and handling them.  Do not put your hands near your face or eyes.  Wash hands thoroughly when finished.  The seeds and inner white membrane contain the highest amounts of capsaicin, so discard these if you prefer a milder form in your recipes.  They can be chopped or diced and added to salsas, soups, or stews.  Cooking will reduce the heat of jalapenos.  Roasting or grilling them will give them a smoky flavor—delicious!