<p>Hessam Azarijafari, Randy Kirchain, and Jeremy Gregory explore how innovations in the concrete industry can reduce greenhouse gas emissions. Image credit: Pexels/Life Of Pix.</p>

How Zen stones form

Welcome to Science Sessions, the PNAS podcast program. Listen to brief conversations with cutting-edge researchers, Academy members, and policymakers as they discuss topics relevant to today's scientific community. Learn the behind-the-scenes story of work published in PNAS, plus a broad range of scientific news about discoveries that affect the world around us.