In 1938 Hahn wrote Meitner about a puzzling find in his continued studies with Strassmann. Hahn and Strassmann had found what appeared to be isotopes of barium in the decay products.

During Christmas break of 1938 Meitner's nephew Otto Frisch  came to visit her. Meitner showed Frisch Hahn's letter to see if he could make sense of it.

Meitner and Frisch decide to take a walk while they think about it. After awhile they sat down on a log and began working calculations on scraps of paper. Meitner suggested that they use the liquid drop model to look at the nucleus.

Upon Meitner's suggestion Frisch explains how a drop would elongate, pinch in the middle, and separate when continually bombarded with particles. Frisch realized this is what had happened with the nucleus and neutrons.

After doing some calculations Meitner and Frisch confirmed that the nucleus had indeed split in two, releasing tons of energy upon splitting.

Frisch took the discovery to America where it was met with great interest. Meitner and Frisch published a paper in Nature. Hahn and Strassmann published a separate paper in which they did not give Meitner any credit.