Finnish Daycares Ditched Pavement for Mud and Dirt. A Month Later, the Blood Tests Stunned Scientists

In Finland, researchers wanted to test a simple idea: what happens to kids’ health if you swap out the pavement, gravel, and plastic in their daycare yards for actual nature?

So, they dug up segments of forest floor and moved them into urban daycare centers. They rolled out grass. They added planter boxes where kids could grow and tend crops, and peat blocks for climbing and digging. Then they waited and ran blood tests.

The results, published in the journal Science Advances and coordinated by the Natural Resources Institute Finland, were striking enough to surprise the scientists themselves.