What Must Be In The Oven Yet Cannot Be Baked? Grows In The Heat Yet Shuns The Light Of Day? What Sinks In Water But Rises With Air? Looks Like Skin,Butisfineashair?

Riddle: What must be in the oven yet cannot be baked? Grows in the heat yet shuns the light of day? What sinks in water but rises with air? Looks like skin,butisfineashair?
Answer: Yeast