The mysterious world of the deep sea has always fascinated humans. Its systematic exploration began in the second half of the 19th century, after initial evidence of its habitation by living organisms was found. Between 1872 and 1876, a British expedition aboard the HMS Challenger documented life in the deep sea using highly advanced scientific equipment and laboratories for that time. The resulting research report, comprising 50 volumes, became the foundation for modern oceanography. In Germany, zoologist William Marshall was one of the leading experts in marine science at that time. In 1888, he published a monograph on deep-sea life that vividly summarizes the methods and results of the British researchers and presents the many discovered life forms in the deep sea.