CRISPR, an acronym for “clustered regularly-interspaced short palindromic repeats,” is at the center of a biotech intellectual-property battle whose outcome, according to The Wall Street Journal, could have a commercial value in the billions of dollars. Earlier this month, proceedings for exactly who owns the rights opened in Virginia. How did this patent fight begin? It’s a tale of two scientists on two coasts.

In March 2013, molecular biologist Dr. Jennifer Doudna from the University of California, Berkeley, filed an application that included 155 claims involving CRISPR with the U.S. Patent & Trademark Office (PTO). Several months later in October 2013, Dr. Zhang of The Broad Institute, affiliated with MIT and Harvard, filed his own claim to the coveted technology. The WSJ notes that while Dr. Doudna filed before Dr. Zhang, the PTO’s review of Dr. Zhang’s application was faster than hers. In 2014, the PTO issued Dr. Zhang a CRISPR patent. After failed negotiations between the two scientists’ sides, Dr. Doudna formally contested Dr. Zhang’s patent claims.

Interestingly, while both scientists were filing their respective applications, a change was taking place in the PTO. No longer would they grant applications to those who could prove developed an idea first, despite when they submitted their application. Instead, whoever filed first was given priority. As the WSJ points out: Is Dr. Zhang, who filed after Dr. Doudna, eligible to be grandfathered under the old rules?

The decision over which scientist will win could take years — several years — as the case for the “gene-editing advancement” makes its way through multiple litigation twists and turns, including potential appeals.