No one can take up the background of the contributions of Niels Bohr to nuclear physics without being reminded at once of the first paper he ever published, “The Determination of the Surface Tension of Water by the Method of Jet Vibration”. It appeared in 1909 when he was 24 years old. It and a second paper on the same subject in the following year marked early stages in Bohr's lifelong interest in liquid drops and their vibrations. Twenty‐eight years later the vibrating fluid sphere found in his hands a new application as a model for nuclear excitations; thirty years later it became his model for nuclear fission.