On 21 December 1872, HMS Challenger set sail from Portsmouth, England, to begin a global voyage of deep-sea exploration, unique for the scale of its ambition and scope. Made possible by technological and scientific developments, extensive international cooperation and supported by a team of researchers and naval officers, the expedition was part of a concerted nineteenth-century drive to map the ocean floors and search for life in the abyss. By the time the ship returned to Britain in 1876, the scientific team on board had amassed what was then the largest collection of examples of life from the deep sea. But their work was not finished and over the next two decades a global network of researchers prepared the results for publication, culminating in a 50-volume series that is considered the intellectual foundation of modern oceanography.