What do the human brain, the Internet and climate change have in common? They're all hugely complex, and while they're very different, the tools used to grapple with this complexity are likely to be similar. We visited the Cambridge complex systems consortium, dedicated to building an over-arching science of complexity, and talked to neuroscientist Ed Bullmore, mathematician Frank Kelly and climate scientist Hans Graf about their take on complexity. This podcast accompanies the article Catching terrorists with maths.