<p><span>Cells in the placenta have an unusual trick for activating gentle immune defenses and keeping them turned on when no infection is present. It involves crafting and deploying a fake virus. Read more at QuantaMagazine.org. Music is “Unanswered Questions” by Kevin MacLeod.</span></p>

In the Gut's 'Second Brain,' Key Agents of Health Emerge

Exploring the distant universe, the insides of cells, the abstractions of math, the complexity of information itself, and much more, The Quanta Podcast is a tour of the frontier between the known and the unknown. In each episode, Quanta Magazine Editor-in-Chief Samir Patel speaks with the minds behind the award-winning publication to navigate through some of the most important and mind-expanding questions in science and math. Quanta specifically covers fundamental research — driven by curiosity, discovery and the overwhelming desire to know why and how. Join us every Tuesday for a stimulating conversation about the biggest ideas and the tiniest details.(If you've been a fan of the Quanta Science Podcast, it will continue here. You'll see those episodes marked as audio edition episodes every two weeks.)