Breathing Fungus
Capture the breath of a fungus!
Yeast is alive. It is made of living cells. Yeast is a fungus, just like mushrooms. We use yeast to bake bread. Fungi provide a critical part of nature's continuous rebirth: fungi recycle dead organic matter into useful nutrients. When you add the warm water, the yeast feeds on the sugar. As it feeds, it breathes. Yeast breathes out carbon dioxide which fills the balloon.
You have now captured yeast breath!