Seashells, stretching from the deep past into the present day, are touchstones leading into fascinating realms of the natural world and cutting-edge science. Members of the phylum Mollusca are among the most ancient animals on the planet. Their shells provide homes for other animals, and across the ages, people have used shells not only as trinkets but also as a form of money, and as powerful symbols of sex and death, prestige and war. The science and natural history of shells are woven into a compelling narrative, revealing their cultural importance and the ways they have been used by humans over the millennia. (Seashells have even been tapped as a source of mind-bending drugs.) Marine biologist Helen Scales shows how seashells have been sculpted by the fundamental rules of mathematics and evolution; how they gave us color, gems, food, and new medicines. After surviving multiple mass extinctions millions of years ago, molluscs and their shells still face an onslaught of anthropogenic challenges, including climate change and corrosive oceans. But rather than dwelling on all that is lost, Scales emphasizes that seashells offer an accessible way to reconnect people with nature, helping to bridge the gap between ourselves and the living world. Spirals in Time: The Secret Life and Curious Afterlife of Seashells shows why nature matters, and reveals the hidden wonders that you can hold in the palm of your hand.