In this episode, Professor Brian Cox shows how Earth's basic ingredients, like the pure sulphur mined in the heart of a deadly volcano in Indonesia, have become the building blocks of life. Hidden deep in a cave in the Dominican Republic lies a magical world created by the same property of water that makes it essential to life. Clinging to a precipitous dam wall in Italy, baby mountain goats seek out Earth's chemical elements essential to their survival. In the middle of the night in a bay off Japan, Brian explains how the dazzling display of thousands of glowing squid shows how life has taken Earth's chemistry and turned it into the chemistry of life.
A close-up view of sex, bug-style, as David Attenborough talks viewers through the different ways in which creepy-crawlies reproduce. Size matters for the minuscule male orb spider, creepily sneaking up on its intended and trying to mate without her noticing, while there's no rest for the lothario-like butterfly, which has plenty of notches on its proverbial bedpost. However, the harvestman spider has no use for sex at all, and reproduces by cloning itself.
While most of the series has focused on conflict, this episode is all about co-operation. The suitably named social spiders spin one enormous, 30m web for the whole colony, a queen bee rules her hive with a strict hierarchy and some green ants show great team spirit to help build a nest together. There are no broken societies here. David Attenborough shifts the focus to bugs that prefer cooperation rather than conflict. They include burrowing cockroaches, the suitably named social spiders - which share a 30-metre web.