Can we bridge the divide between 'us' and 'them'? At a time when the whole world seems to be polarizing into irreconcilable camps, Morgan Freeman sets out on a journey in search of the forces that push us apart, from intolerance of differences to fear of outsiders, and the possibilities of coming together.

Brian travels across the US and encounters some astonishing creatures that reveal how the senses evolved. It is a story that takes him through life's journey, from single-celled organisms to sentient beings.

Dr Michael Scott looks at the dramatic decline of Athens and the remarkable triumph and transformation of theatre. During the 4th century BC Athens would lose its Empire, its influence and even its democracy. But theatre, that most Athenian of inventions, would thrive, spreading throughout the Greek world and beyond and giving rise to a new kind of comedy, one so popular and prevalent that it is still at the heart of our comedy today.

Electricity is not just something that creates heat and light, it connects the world through networks and broadcasting. After centuries of man's experiments with electricity, the final episode tells the story of how a new age of real understanding dawned - how we discovered electric fields and electromagnetic waves. Today we can hardly imagine life without electricity - it defines our era. As our understanding of it has increased so has our reliance upon it, and today we are on the brink of a new breakthrough, because if we can understand the secret of electrical superconductivity, we could once again transform the world.

Tim Whewell is in St Petersburg to meet the self-styled Russian nationalists and patriots who are volunteering to join the fighting in eastern Ukraine. He joins a group of volunteers as they undertake military training, and travels to Ukraine to see how the volunteer force is fighting on the ground.

Trade, and in particular trade in luxury goods, drove the commerce economies of the Bronze Age. This is the time when the first super powers in history, Egypt and Mesopotamia, emerge and dominate the 'world' stage of the Mediterranean and Aegean seas and surrounding areas.