A spore is a tiny reproductive cell that some living things use to spread and create new organisms. Think of spores as nature's microscopic seeds, though they work quite differently from the seeds you might plant in a garden.

Fungi like mushrooms release millions of spores into the air, so small you can't see individual ones without a microscope. When a spore lands in the right spot with enough moisture and warmth, it can grow into a whole new mushroom. Ferns also reproduce through spores rather than seeds or flowers. If you look under a fern's leaves, you might see tiny brown dots: those are clusters of spores ready to spread.

Spores are incredibly tough and can survive harsh conditions that would kill most living things. Some bacterial spores can endure extreme heat, cold, or dryness for years, waiting for the right moment to grow. This toughness makes spores difficult to eliminate, which is why hospitals work so hard to sterilize their equipment.

Scientists have found ancient spores preserved in ice and amber, some millions of years old, helping simple plants spread across the planet hundreds of millions of years ago.