Why does bread get moldy?
For grown-ups: the science
Bread gets moldy when tiny mold spores in the air land on it and grow.
Molds are fungi. Airborne spores can germinate on bread when moisture, suitable temperature, oxygen, and nutrients are available. The visible fuzzy growth is mainly fungal hyphae and spore-producing structures; growth often extends beyond what is visible, so moldy bread should be discarded rather than having spots removed.
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Transcript
A loaf of bread sits on the kitchen counter. Why can fuzzy spots grow on it?
Mold starts from tiny spores floating in the air. Spores are like seeds that can grow into mold.
When spores land on damp bread, they can wake up and grow. Bread gives them water and food.
The mold spreads tiny threads through the bread. The fuzzy patch is the part we can see.
So bread gets moldy when tiny spores find a warm, damp place with food.