S1, E3: The forces of nature make Earth a restless planet but they also made it a home for life. To understand how something so complex could emerge from a barren rock we first need to understand what our planet is made of. In this episode, we look at the elements. On the Kawah Ijen volcano in Indonesia, firefighters battle to protect the purity of the sulfur that boils to the surface. Beneath the green grass of the Great Rift Valley in Tanzania, rock is stained red by iron because elements react and combine with each other to create molecules. In a cave system in the Dominican Republic we see, a halocline, created by water's power to dissolve. In Italy, Alpine ibex make an astonishing climb up the near-vertical face of the Cingino Dam to lick essential salts and minerals that have evaporated on the rocky wall. The chemistry of life, the reactions between Earth's elements, use and create energy. Off the coast of Toyama Bay in Japan each spring, millions of firefly squid rise up from the deep ocean to spawn, their bodies glowing with a dazzling pattern of blue lights created by life's alchemy. But it is another piece of chemistry that we think was the first step in our planet's journey from ball of rock to a living world. In a fjord off the coast of iceland, a hydrothermal vent soars up from the sea bed. A simple experiment shows how this water creates power. It is the same mechanism that is found throughout the living world and powers every cell in our body. This leads to the intriguing possibility that our most ancient ancestor wasn't a living thing at all but a hydrothermal vent at the bottom of an ancient ocean.