Daniel wants to know why Swiss cheese has holes in it.

The answer involves bacteria, gas bubbles, and a mystery that took scientists over a hundred years to fully solve.

The holes -- called eyes by cheesemakers -- form when bacteria inside the cheese produce carbon dioxide during ripening. That gas needs somewhere to form. And what it forms around turned out to be the surprising part. Swiss researchers confirmed it in 2015 using controlled experiments and CT scanning.

A cheese with no holes is called blind. A master cheesemaker can read the eyes the way a doctor reads an X-ray.

What you will find in this episode:

• Why bacteria produce the gas that forms the holes
• What the holes are actually called -- and what a cheese with no holes is called
• The mystery that scientists couldn't explain for over a  ...