a Frontline co-production with Hedrick Smith Productions ; WGBH Educational Foundation ; Frontline executive producer, David Fanning ; senior producer, Hedrick Smith ; producer, Marc Shaffer ; written by Hedrick Smith and Rick Young ; director, Rick Young
director, Elise Swerhone ; written by Robert Lower ; producers, Merit Jensen Carr, Sandra Moore ; a Merit Motion Pictures production ; produced in association with Canadian Broadcasting Corporation ; produced in association with National Geographic Channel, and with the participation of Discovery Science
directed and written by Mike Downie ; produced by Tina Verma ; produced by Canadian Broadcasting Corporation, in association with National Geographic Channel, and with the participation of Discovery Science
produced by NHNZ in association with PBS, ARTE France, CCTV9, Discovery Networks Europe, ZDF, ZDF Enterprises and NHK ; producers, John Cullum, Hayes Baxley, and Quinn Berentson ; writers, Craig Meade, John Cullum, Andrew Murray, Mark Everton, and Gary Parker
directed by Harald Pokieser ; narrated by Natalia Reyes ; produced by Austrian Broadcasting Corporation Radio & Television (ORF), Cosmos Factory, NDR Naturfilm, Public Broadcasting Service, ARTE, DocLights
produced by NHNZ in association with PBS, ARTE France, CCTV9, Discovery Networks Europe, ZDF, ZDF Enterprises and NHK ; producers, John Cullum, Hayes Baxley, and Quinn Berentson ; writers, Craig Meade, John Cullum, Andrew Murray, Mark Everton, and Gary Parker
produced by NHNZ in association with PBS, ARTE France, CCTV9, Discovery Networks Europe, ZDF, ZDF Enterprises and NHK ; producers, John Cullum, Hayes Baxley, and Quinn Berentson ; writers, Craig Meade, John Cullum, Andrew Murray, Mark Everton, and Gary Parker