The Amazon told as a building, for children aged 6 to 8, hosted by Ben, an eight-year-old boy who climbs it alongside the child. The course does not ask where the forest is — it asks AT WHAT HEIGHT. It opens with a cutaway of four storeys: the forest floor up to about five metres, the understorey up to twenty, the canopy from twenty to forty, and the emergents past forty, with a river standing up through all four. Then it lights one storey per episode and shows who lives there and why: the tapir on the floor, swallowing big seeds whole and dropping them kilometres away in the darkest storey of all; the three-centimetre glass frog in the understorey, with a transparent belly and a trick of storing her own red blood in her liver so she can sleep invisible; the white-throated toucan in the canopy, with a bill over twenty centimetres that is hollow, light as a bridge lattice and doubles as a radiator; the harpy eagle and the fifty-metre brazil nut tree above everybody, held up by a big bee and an agouti; and finally the river, which rises the height of a building once a year so that fish swim among the branches and plant trees. Everything hangs on one number: only about two per cent of the sunlight ever reaches the forest floor.