We’re ready to get our hands dirty as we explore the stuff beneath our feet. Clay, sand, mud — soil is everywhere. And it’s alive! We’ll find out how it helps plants grow and learn about all the little organisms that are invaluable in the process (hint: it involves something called the “poop loop”). Plus: A brand new Moment of Um answers the question: “What’s inside of a tooth?” Today’s episode is sponsored by the CBC podcast Tai Asks Why and Quip (getquip.com/brainson). You can support Brains On at brainson.org/donate

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