Humans are so clever they’ve built their own habitat, designed to keep wild nature out. Yet as we discover the urban environment is totally dependant on the natural world. Over the three years of filming for Human Planet, the teams have spent time with over seventy different communities in countries across the planet. Despite seeing many different ways of living, there are some aspects of family life that remain the same whether you live in a tree house in West Papua, or a brick house in Bolton. These similarities became very clear when the urban team went to film on a rubbish dump in Kenya. Here on the Kibarani dump on the outskirts of Mombasa, Ali, Ashe and their family live and survive amongst the rubbish, and even here, just like anywhere on the planet, everything stops for a nice cup of tea!

Here, Aleks charts how the Web is forging a new brand of politics, both in democracies and authoritarian regimes. With contributions from Al Gore, Martha Lane Fox, Stephen Fry and Bill Gates, Aleks explores how interactive, unmediated sites like Twitter and YouTube have encouraged direct action and politicised young people in unprecedented numbers. Yet, at the same time, the Web's openness enables hardline states to spy and censor, and extremists to threaten with networks of hate and crippling cyber attacks.

In episode two, Professor Brian Cox is off to India, where he assesses arguably the first evidence of rational thought in literature, the poetry of the Vedic monks. They pondered mankind's origins, realising there must have been a day with no yesterday - a day of creation - prompting the age-old question of where did the universe come from? Brian marvels that the universe seems to follow a set of rules, the laws of physics, allowing space to be considered on the grandest scale, travelling to the most distant, farthest reaches of the cosmos just by using our minds. Brian also visits Japan, and offers viewers the idea that man lives in just one of an infinite number of universes that are being made all the time.

Raging Teens follows a group of young boys and girls throughout their teenage years and captures the changes that the body undergoes through puberty. Its main focus, however, is on Beatrice and the changes she undergoes such as shopping, growing breasts, pubic hairs and her first period (her mother bought her some Chocolate Éclairs to help celebrate which must be a British thing). The boy's side covers testosterone and what changes it spurs in a lad's body such as facial hair, their voice cracking at the wrong time, and parts of the body that have until now lain dormant. You also learn that a pubic hair only grows for 6 months, which keeps it short, and is actually flat oval and not round which is why they curl.

The Milky Way, our galaxy, is a magnificent sight in the night sky, but we know surprisingly little about it for certain. What is its shape? How many stars does it actually contain? What lies at its centre? The Gaia space telescope will answer these questions, being armed with the most advanced camera to leave our planet, and it will allow us to see our galaxy as we've never seen it before. The Sky at Night visits the factory in Chelmsford that made the astonishing sensor at the heart of the mission.

In this second episode we travel from January to the March equinox. Kate Humble gets closer to the Sun than she has ever been before, whilst Helen Czerski visits a place that gets some of the biggest and fastest snowstorms on Earth.