Timothy Walker, director of Oxford University Botanic Garden, reveals how the breakthroughs of Swedish botanist Carl Linnaeus, Chelsea gardener Phillip Miller and English naturalist John Ray created the science of botany.

The air we breathe, and all the food we eat, is created from water, sunlight, carbon dioxide and a few minerals. That's it, nothing else. It sounds simple, but this process is one of the most fascinating and complicated in all of science. Without it there could be no life on Earth.

For 10,000 years or more, humans created new plant varieties for food by trial and error and a touch of serendipity. Then 150 years ago, a new era began. Pioneer botanists unlocked the patterns found in different types of plants and opened the door to a new branch of science - plant genetics.