A rainforest is a thick, hot, very wet forest full of more kinds of plant and animal than almost anywhere else on Earth. A single hectare of Malaysian rainforest - about the size of two football pitches - can hold over 200 different kinds of tree. The same patch in a British wood might have ten.
The forest is built in layers like a tall building. At the very top, the 'emergent' giants poke their heads above everything else. Below them is the 'canopy', a green roof where most of the animals live. Lower down is the dim 'understory', and at the bottom, the dark, leafy 'forest floor'. Each layer has its own creatures.
These forests stayed alive for so long because Malaysia missed the great ice ages that froze most of the rest of the world. While other forests were wiped out by ice, these ones just kept on growing. Many of the plants and animals here are 'living fossils' - their family designs have barely changed for millions of years.
Malaysia protects its rainforests in big national parks. Taman Negara, on the mainland, lets visitors walk along the Canopy Walkway - a long swinging rope bridge stretched between huge trees, 40 metres up. You walk through the treetops, where the monkeys and the hornbills are.