Until World War II, Latino immigration to the United States was overwhelmingly Mexican-American. Now three new waves bring large-scale immigration from Puerto Rico, Cuba, and the Dominican Republic. As the Puerto Rican government implements a historic overhaul over a million Puerto Ricans are encouraged to leave for the US mainland, to alleviate the economic pressure. A young Juanita Sanabria arrives in New York, works hard in the garment district, but encounters hostility and discrimination. Ethnic tensions explode in youth gang warfare depicted in films like West Side Story, etching the stereotype of the knife wielding Puerto Rican in the American consciousness.

Sagan reflects on the future of humanity and the question of 'who speaks for Earth?' when meeting extraterrestrials. He discusses the very different meetings of the Tlingit people and explorer Jean-François de La Perouse with the destruction of the Aztecs by Spanish conquistadors, the looming threat of nuclear warfare, and the threats shown by destruction of the Library of Alexandria and the murder of Hypatia. The episode ends with an overview of the beginning of the universe, the evolution of life, and the accomplishments of humanity and makes a plea to mankind to cherish life and continue its journey in the cosmos. The Cosmos Update notes the preliminary reconnaissance of planets with spacecraft, the fall of the Berlin Wall and the end of apartheid in South Africa, and measures towards the reduction of nuclear weapons.

Comedian Ben Miller returns to his roots as a physicist to try to answer a deceptively simple question: what is one degree of temperature? His quest takes him to the frontiers of current science as he meets researchers working on the hottest and coldest temperatures in the universe, and to a lab where he experiences some of the strangest effects of quantum physics - a place where super-cooled liquids simply pass through solid glass. Plus, Ben installs his very own Met office weather station at home. Ben's investigations in this personal and passionate film highlight the importance of measurement and accuracy in the 21st century.

Mammals dominate the planet. They do it through having warm blood and by the care they lavish on their young. Weeks of filming in the bitter Antarctic winter reveal how a mother Weddell seal wears her teeth down keeping open a hole in the ice so she can catch fish for her pup. A powered hot air balloon produces stunning images of millions of migrating bats as they converge on fruiting trees in Zambia, and slow-motion cameras reveal how a mother rufous sengi exhausts a chasing lizard. A gyroscopically stabilised camera moves alongside migrating caribou, and a diving team swim among the planet's biggest fight as male humpback whales battle for a female.

The world of invertebrates exists in a web of relationships with plants and other animals. Unique footage of the world's smallest insect (a fairy wasp only quarter of a millimetre long) shows it flying underwater to find the eggs of water beetles in which to lay its own brood. Some ants 'farm' the trees that give them shelter, creating areas known as 'Devil's gardens'. To make sure these grow without competition, they kill off other seedlings in the surrounding vegetation. The blister beetle's larvae huddle together on the end of a piece of grass and mimic a female bee. When a male bee tries to mate with the 'female', the larvae grab on to his belly. Confused, he flies away and searches for a real female. When he eventually finds her and mates with her, the beetle larvae hurriedly swap from his front on to her back, and hence get carried back to her nest where they eat her pollen supplies.

The inside story of how a small band of fanatical jihadi fighters became the world's richest terror army ever. Featuring the first major TV interview with an imprisoned senior leader of the self-proclamed Islamic State, Peter Taylor looks behind its medieval savagery and investigates how it became so fabulously rich and resilient.