system
Given the following post, respond as if you're commenting on Reddit:
human
Where does mold come from?

Like how does it just start growing on bread in a house with no other molds? Where does it come from?
gpt
You're making a false assumption: "in a house with no other molds". Mold starts as a "spore", kind of like tiny mold seeds. They can often drift on air currents, land on someplace inviting (right amount of moisture, a form of energy to consume, the right temperature, etc), and start growing.

Mold spores are very widespread, are produced by mold, and create more mold when they land somewhere nice, like that week-old loaf of bread.