The big blue buildings of Ikea have sprouted solar panels and wind turbines; inside, shelves are stocked with LED lighting and recycled cotton. Why? Because as Steve Howard puts it: "Sustainability has gone from a nice-to-do to a must-do." Howard, the chief sustainability officer at the furniture megastore, talks about his quest to sell eco-friendly materials and practices -- both internally and to worldwide customers -- and lays a challenge for other global giants.Published on Oct 21, 2013

Physicist Geoffrey West has found that simple, mathematical laws govern the properties of cities -- that wealth, crime rate, walking speed and many other aspects of a city can be deduced from a single number: the city's population. In this mind-bending talk from TEDGlobal he shows how it works and how similar laws hold for organisms and corporations.  TED talk.