Ms. Hansen and the Explorers are very interested in learning--they want to know everything they can about the human body. But they aren"t alone! The Zelmans, Xeni and Zeno, have come from their planet to learn about Earth"s beings too! They travel into the respiratory system into the lungs" alveoli to learn how the lungs exchange oxygen for carbon dioxide. Come along as the Explorers and their favorite guests tour the human lungs.