Sir David Attenborough's hushed but excited tones have been heard in living rooms around the world.
Here are some of his most memorable quotes:
1. "It seems to me that the natural world is the greatest source of excitement; the greatest source of visual beauty; the greatest source of intellectual interest. It is the greatest source of so much in life that makes life worth living."
2. "I just wish the world was twice as big and half of it was still unexplored."
3. "The question is, are we happy to suppose that our grandchildren may never be able to see an elephant except in a picture book?"
4. "It is vital that there is a narrator figure whom people believe. That's why I never do commercials. If I started saying that margarine was the same as motherhood, people would think I was a liar."
5. "You know, it's a terrible thing to appear on television, because people think you actually know what you're talking about."
6. "I don't run a car, have never run a car. I could say that this is because I have this extremely tender environmentalist conscience, but the fact is I hate driving."
7. "If I can make programmes when I'm 95, that would be fine. But I would think I'll have had enough by then."
8. "You have to steer a course between not appalling people, but at the same time not misleading them."
9. "I don't think we are going to become extinct. We're very clever and extremely resourceful - and we will find ways of preserving ourselves, of that I'm sure. But whether our lives will be as rich as they are now is another question."
10. "An understanding of the natural world and what's in it is a source of not only a great curiosity but great fulfilment."
11. "Our planet may be home to 30 million different kinds of animals and plants. Each individual locked in its own lifelong fight for survival. Everywhere you look, on land or in the ocean, there are extraordinary examples of the lengths living things go to to stay alive."
12. "Ever since we arrived on this planet as a species, we've cut them (plants) down, dug them up, burnt them and poisoned them. Today we're doing so on a greater scale than ever."
13. "There are some four million different kinds of animals and plants in the world. Four million different solutions to the problems of staying alive."
14. "Reptiles and amphibians are sometimes seen as simple, primitive creatures. That's a long way from the truth. The fact that they are solar-powered means that their bodies require only 10% of the energy that mammals of a similar size require. At a time when we ourselves are becoming increasingly concerned about the way in which we get our energy from the environment and the wasteful way in which we use it, maybe there are things that we can learn from Life in Cold Blood.
15. "A hundred years ago, there were one-and-a-half billion people on Earth. Now, over six billion crowd our fragile planet. But even so, there are still places barely touched by humanity."
Inspiring Attenborough: Sir David At 90 will be broadcast on BBC One on May 8