Yeast are eukaryotic microorganisms in the fungi kingdom. This unicellular fungus is commonly used in baking to create rising. When the yeast feeds on sugars in flour, it expels carbon dioxide in the process. The students set up an experiment with three different bottles, each one containing a different food source for the yeast to feed on; sugar, mountain dew and baking powder. After 15 minutes, the students measure the circumference of the balloon to discover which food source the yeast ate the most of. The more the yeast eats, the more carbon dioxide that is expelled into the balloon. The children predict, experiment, collect data, analyze and explore if their hypothesis was supported.