When she was in the fifth grade, Nicole Gaudelli told her father she wanted to become a doctor to help people. He replied, “Why don’t you become a scientist?”

“Scientists can help even more people” with their discoveries, she remembers him explaining.

By the time Gaudelli joined Harvard University chemist David Liu’s lab as a postdoctoral researcher in 2014, she had published only two scientific papers, but it didn’t take long before she invented a tool that could someday treat hundreds, even thousands of diseases.

Soon after Gaudelli arrived, another postdoc, named Alexis Komor, joined the Liu lab with plans to invent a new version of the gene-editing tool CRISPR. The original CRISPR system simply cuts DNA like a pair of scissors, allowing researchers to turn off an errant gene. Komor’s so-called base editor worked more like an eraser and pencil, changing a single letter of DNA to another—a cytidine (C) to a thymidine (T).

While assisting Komor with the experiment, Gaudelli began planning a second base editor to swap DNA’s other two letters, adenosine (A) and guanosine (G).

Gaudelli’s proposed adenine base editor could theoretically fix nearly 50% of the single-letter DNA mutations known to cause disease in humans, accounting for thousands of genetic diseases. But while Komor’s editor was built by combining existing proteins, Gaudelli’s version required evolving a protein to perform a chemical reaction that doesn’t exist in nature.

That broke an 18-year-old Liu lab rule to avoid projects in which the first step requires evolving the starting material. “Honestly, I thought it was never going to work,” Gaudelli says. “But the technology’s potential was so overwhelmingly high that it was worth it.”

After a year of tenacious work, Gaudelli was successful. She spent an additional year refining the base editor before publishing the results. Then Harvard licensed the base editors to a new biotech start-up called Beam Therapeutics, which Liu cofounded.

Remembering her conversation with her father, Gaudelli decided to forgo her plans to join academia and instead joined Beam to help transform her invention into a medicine for treating genetic diseases.

“It’s classic Nicole,” Liu says. “Making sure the fruits of her labor actually help others and don’t just end up on the pages of a journal.”