This is a glass globe with a lip on one side and a hole on the other. A balloon fits over the lip and hangs inside the globe. A cork may or may not be placed in the hole on the other side. Without the cork, the balloon is inflated the normal way. With the cork, it cannot be inflated. The balloon may be inflated by sucking on the hole. This demonstrates the passive way lungs inflate and give insight into collapsed lungs. Water may be put in the plugged hole inflated balloon. Be sure to hold it over a sink when pulling the plug.