The Natural History Museum is a very interesting place to visit. It is absolutely vast, and I always come away knowing something that I didn't before.
There are four areas: Blue zone, Red zone, Green zone and Orange zone. The Blue zone has exhibits on all living creatures including the dinosaurs. The Red zone covers the Earth including sections on earthquakes and volcanos as well as glittering gemstones. The Green zone is about life on our planet and among other things covers evolution, fossils, bugs and the environment.
The front can often have large queues, and although they don't usually take long to get inside, it is worth checking the side entrance as this can have no queue at all.