Scientists have finally figured where Swiss cheese holes come from, and why they're disappearing

The mystery of what makes the iconic holes in Swiss cheese --and why they're disappearing-- has finally been solved.

A Swiss agricultural institute discovered that tiny specks of hay are responsible for the famous holes in cheeses like Emmental or Appenzell.

In a report released Thursday, Agroscope and the Swiss Federal Laboratories for Materials Science and Technology said in a statement that these "microscopically small hay particles" help create the holes in the traditional Swiss cheese varieties.

And the reason why we've see less of these holes over the last 15 years is because of the transition from age-old milking methods in barns to fully-automated, industrial milking systems, which is cleaner.

Agroscope spokesman Regis Nyffeler told The Telegraph said that today's modern milking machines send the milk straight to a filter, unlike the before traditional methods that collected milk in a bucket.

In a series of tests, scientists added different amounts of hay dust to the milk and discovered it allowed them to regulate the number of holes.

Agroscope said that the fascination with the formations in the cheese stretches back to 1917 when a detailed review of Emmental was published by American William Clark. He contended they were produced because of carbon dioxide from bacteria.

The Associate Press contributed to this report.