In the third programme of the series, Aleks gives the lowdown on how, for better and for worse, commerce has colonized the web - and reveals how web users are paying for what appear to be 'free' sites and services in hidden ways. Joined by some of the most influential business leaders of today's web, including Eric Schmidt (CEO of Google), Chad Hurley (CEO of YouTube), Bill Gates, Martha Lane Fox and Reed Hastings (CEO of Netflix), Aleks traces how business, with varying degrees of success, has attempted to make money on the web. She tells the inside story of the gold rush years of the dotcom bubble and reveals how retailers such as Amazon learned the lessons. She also charts how, out of the ashes, Google forged the business model that has come to dominate today's web, offering a plethora of highly attractive, overtly free web services, including search, maps and video, that are in fact funded through a sophisticated and highly lucrative advertising system which trades on what we users look for. Aleks explores how web advertising is evolving further to become more targeted and relevant to individual consumers. Recommendation engines, pioneered by retailers such as Amazon, are also breaking down the barriers between commerce and consumer by marketing future purchases to us based on our previous choices. On the surface, the web appears to have brought about a revolution in convenience. But, as companies start to build up databases on our online habits and preferences, Aleks questions what this may mean for our notions of privacy and personal space in the 21st century

Of all the wonders of the human body, there's one more mysterious than any other. Blood: five precious litres that keep us alive. Yet how much do we really know about this sticky red substance and its mysterious, life-giving force? Michael Mosley gives up a fifth of his own blood to perform six bold experiments". From starving it of oxygen to injecting it with snake venom, Michael reveals the extraordinary abilities of blood to adapt and keep us alive. Using specialist photography, the programme reveals the beauty in a single drop. Michael even discovers how it tastes when, in a television first, he prepares a black pudding with his own blood. Down the ages, our understanding of blood has been as much myth as science, but Michael reveals there might be truth in the old vampire legends, as he meets one of the scientists behind the latest research that shows young blood might be able to reverse the ageing process - the holy grail of modern medicine.

Fresh water is our most precious resource and it defines the distribution of life on land. Follow the descent of rivers from their mountain sources to the sea. Watch spectacular waterfalls, fly inside the Grand Canyon and explore the wildlife below the ice in the world's deepest lake. Witness unique and dramatic moments of animal behaviour: a showdown between smooth-coated otters and mugger crocodiles; deep-diving long tailed macaques; massive flocks of snow geese on the wing and a piranha frenzy in the perilous waters of the world's largest wetland.

Adam Rutherford meets a new creature created by American scientists, the spider-goat. It is part goat, part spider, and its milk can be used to create artificial spider's web. It is part of a new field of research, synthetic biology, with a radical aim: to break down nature into spare parts so that we can rebuild it however we please. This technology is already being used to make bio-diesel to power cars. Other researchers are looking at how we might, one day, control human emotions by sending 'biological machines' into our brains.

1916. The war is raging in Europe and stretches from the trenches in France to the Italian Alps and the Balkans, and beyond to the gates of the Eastern world. The conflict becomes industrial, and millions of shells rain down on the battlefields; Verdun and the Somme are the deadliest battles in this second year of the war. Who can stop this infernal machine?

The documentary is about the effect of fossil fuels on issues such as global warming, the environmental crisis, society and the questionable practices of oil companies. It examines the interconnection of human domination of the planet and the use of petroleum, and offers solutions for how we can stop our progression down this destructive path. Written and directed by James Jandak Wood. The film has several awards and nominations