What is life?

From bacteria to biosphere, the evolution of life took a convoluted course. Science illuminates this path.

We live. We—people, birds, flowering plants, even algae glowing in the ocean at night—differ from rocks, steel, inanimate matter.

We are alive. But what does it mean to live, to be alive, to be a discrete being at once a part of the universe and separated from it by our skin?

What is life?

One of the world's foremost life scientists, author of Symbiosis and Cell Evolution, and an early proponent of the Gaia theory, Lynn Margulis shares her thoughts on this age-old question.