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

In the National Geographic tradition of powerful natural-history images and storytelling, this film reveals once-invisible dimensions of nature that are filled with beauty and wonder-and hold secrets crucial to our survival. It shines a fascinating spotlight on objects and events that escape the naked eye every minute of every day. Visually stunning and rooted in cutting-edge research, the film blends high-speed and time-lapse photography, electron microscopy and nanotechnology.

Corey Feldman (star of Friday the 13th: The Final Chapter) narrates Crystal Lake Memories, which features interviews with approximately 150 cast and crew members from all twelve Friday the 13th films and the syndicated television series, many of whom have never before appeared in on-camera interviews. Interview subjects include Kane Hodder, Robert Englund, Tom Savini, Danielle Panabaker, Sean S. Cunningham, Derek Mears, Betsy Palmer, Wes Craven, Robert Shaye, Alice Cooper and many more

We now know that the brain - the organ that more than any other makes us human - is one of the wonders of the universe, and yet until the 17th century it was barely studied. The twin sciences of brain anatomy and psychology have offered different visions of who we are. Now these sciences are coming together and in the process have revealed some surprising and uncomfortable truths about what really shapes our thoughts, feelings and desires. And the search to understand how our brains work has also revealed that we are all - whether we realise it or not - carrying out science from the moment we are born.

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.

Professor Jim Al-Khalili discovers the intriguing story of how we discovered the rules that drive the universe. Energy is vital to us all, but what exactly is energy? In attempting to answer this question Jim investigates a strange set of laws that link together everything from engines to humans to stars. It turns out that energy, so critical to daily existence, actually helps us make sense of the entire universe.