BRAIN
"The human brain is large and in charge. It controls everything you do -- breathing, eating, reading this sentence. Everything. Humans have the largest brain for their body size in the animal world. Our closest relatives, chimpanzees, cannot perform tasks beyond those of an average toddler. What makes us so smart?"

EYES
"Vision is the team captain of the five senses. Hearing, tasting, smelling, and feeling are important. But most humans get most of their information about the world through their eyes. The first "eyes" in nature appeared on sea animals hundreds of millions of years ago. They were just light-sensitive patches on the skin. But sensing light was so handy for survival that true vision began to. . . "

HEART
"As you read this, your heart is pumping about five quarts of blood throughout your body. The blood is traveling through more than 60,000 miles of blood vessels (arteries, veins, capillaries). That's enough to circle the equator twice, and then some! A heart works tirelessly over a lifetime. During an average life span, the heart beats three billion times without a single break. Not bad for a. . . "

LUNGS
"They're squishy like sponges and stretchy like balloons. You use them every day - and night, too - no matter what you're doing. And, most likely, you never even think about them. They're you're lungs - those elastic bags with millions of tiny air pouches inside. All day long, those sacs in your chest fill and empty with the breath that feeds your body the oxygen it needs to stay alive. But, breathing isn't the only way these pouches help you be you."