Today roads, sidewalks, bridges, and skyscrapers are made of a material called concrete. There's three tons of it for every person on Earth. It's also played a surprisingly large role in rising global temperatures over the last century. So, what exactly makes concrete problematic, and what can we do to fix it? Explore how scientists are working to create a cleaner, more sustainable concrete. [Written by Elizabeth Cox and George Zaidan, directed by Lisa LaBracio, narrated by Jack Cutmore-Scott, music by André Aires].