Investigating the powers of yeast

We listed all the things we thought we would need for our dough.  But what about the yeast? 

What's yeast? Why do we need it?

 

I know let's wake up the yeast with some warm water and make it active!  Then let's feed it some sugar and see what happens next.

The yeast gave off a gas called CO2 and the water went frothy on the top.  The gas blew up our balloons. In bread it makes have the holes we saw some already cooked bread.