STOCKHOLM: US scientists Victor Ambros and Gary Ruvkun have won this year's Nobel Prize in Medicine for the discovery of microRNA, a new class of tiny RNA molecules that play a crucial role in gene regulation, Sweden's Karolinska Institute announced on Monday, German Press Agency (dpa) reported. "This year's Nobel Prize honours two scientists for their discovery of a fundamental principle governing how gene activity is regulated," the institute said in a press release. 'Victor Ambros and Gary Ruvkun were interested in how different cell types develop.' Their "groundbreaking" discovery of microRNA revealed 'a completely new principle of gene regulation that turned out to be essential for multicellular organisms, including humans.' Source: Emirates News Agency