STOCKHOLM − U.S. scientists Victor Ambros and Gary Ruvkun won the 2024 Nobel Prize in Medicine for the discovery of microRNA and its crucial role in how multicellular organisms grow and live, the award-giving body said Monday.

The Nobel assembly said in a statement that the laureates discovered the new class of tiny RNA molecules, which play a crucial role in gene regulation.

The new class of tiny RNA molecules, discovered by Ambros and Ruvkun in the 1980s, play a crucial role in gene regulation, the Nobel assembly said.

"Their groundbreaking discovery revealed a completely new principle of gene regulation that turned out to be essential for multicellular organisms, including humans," the assembly said.

Their work helped explain how cells specialize and develop into different types, such as muscle and nerve cells, even though all the cells in a person contain the same set of genes and instructions for growing and staying alive.

Thomas Perlmann, secretary of the Nobel committee for physiology, said he had reached Ruvkun by phone, waking him up early in the morning in the U.S, but he was eventually happy and "very enthusiastic." He had not yet reached Ambros, he said.

"(Ruvkun's) wife answered. It took a long time till he came to the phone and he was very tired," Perlmann said at a news conference.

Ambros is a professor at the University of Massachusetts Medical School, and Ruvkun is a professor at Harvard Medical School and affiliated with Massachusetts General Hospital in Boston.

In the late 1980s, Ambros and Ruvkun undertook postdoctorate studies in the laboratory of Robert Horvitz, himself a Nobel Prize winner in 2002, studying a 1mm-long roundworm.

Their discoveries on how certain microRNAs in the roundworm govern growth of organs and tissue was initially dismissed as specific to the species.

Further work published by Ruvkun's research group in 2000, however, showed all animal life had relied on the mechanism for more than 500 million years.

Building blocks of life

MicroRNA comes into play when single-strand messenger RNA − the subject of last year's Nobel Prize in medicine − is decoded and translated into making proteins, the building blocks of all human and animal life.

Messenger RNA, in turn, emerges from the universal blueprint in every cell nucleus, the double-helix DNA.

The winners of the prize for physiology or medicine are selected by the Nobel Assembly of Sweden's Karolinska Institute medical university and receive a $1.1 million prize.

As in every year, the physiology or medicine prize was the first in the crop of Nobels, arguably the most prestigious prizes in science, literature and humanitarian endeavors. The remaining five are set to be unveiled over the coming days.

Created in the will of Swedish dynamite inventor and businessman Alfred Nobel, the prizes have been awarded for breakthroughs in science, literature and peace since 1901. Economics is a later addition.

Past winners of the Nobel medicine prize include famous researchers such as Ivan Pavlov in 1904, most known for his experiments on behavior using dogs, and Alexander Fleming, who shared the 1945 prize for the discovery of penicillin.

Last year's medicine prize was awarded to the runaway favorites Katalin Kariko, a Hungarian scientist, and U.S. colleague Drew Weissman, for discoveries that paved the way for COVID-19 vaccines that helped curb the pandemic.

Steeped in tradition, the science, literature and economics prizes are presented to the laureates in a ceremony on Dec. 10, the anniversary of Alfred Nobel's death, followed by a lavish banquet at Stockholm city hall. Separate festivities attend the winner of the peace prize in Oslo on the same day.