zai jian. >> if you want to know how much a hummingbird weighs, check your pockets.mingbird weighs about what a penny weighs -- less than one tenth of an ounce. but they are hungry little creatures. everyday, they consume more than their weight in nectar. for us, that's like eating more than 33 large pizzas in a day. >> they are three little letters, but they can spell the difference between life and death -- cpr. i'll explain what they stand for. >> medical emergencies happen. that's why knowing what to do is so important. ♪ >> what is "cpr?" >> cpr stands for cardiopulmonary resuscitation and that's a really big term that basically means cardio -- heart; pulmonary -- lungs, resuscitation -- try to bring back. we provide a combination of chest compressions and rescue breaths to manually circulate blood throughout somebody's body. because when they are in cardiac arrest it means their heart's not working, so we need to work for it. >> is it something that we all can learn? >> absolutely, in a real red cross course when you take the full thing, you learn how to give b