It’s one of nature’s most perfect contradictions: a substance that is ubiquitous but unseen; humble but essential; surprisingly strong but profoundly fragile. It nurtures life and death; undergirds cities, forests and oceans; and feeds all terrestrial life on Earth. It is a substance few people understand and most take for granted. Yet, it is arguably one of Earth’s most critical natural resources—and humans, quite literally, owe to it their very existence.