By Alexandra Sifferlin
August 6, 2015

Over 30 years ago, Dr. Howard W. Jones Jr. paved the way for the creation of families in the U.S. once thought to be impossible.

Jones, who died July 31 at 104, advanced in vitro fertilization (IVF) and, in collaboration with his late wife Dr. Georgeanna Seegar Jones, was responsible for the birth of the first test-tube baby in the U.S., in 1981. A trailblazer for reproductive medicine, he also performed some of the first sex-change operations.

Despite being over 100, Jones worked regularly until he was hospitalized in July. He died of respiratory failure. “If I have a legacy,” he once said, “it’s of someone who … did not have any qualms about proceeding with the unknown because it was fun to do.”

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This appears in the August 17, 2015 issue of TIME.

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