CRISPR (clustered regularly interspaced short palindromic repeats) is a 
prokaryotic immune surveillance system that is used by bacteria to recognize 
genetic material of infectious organisms, such as phage viruses. Using 
CRISPR-associated (Cas) proteins, this system cleaves foreign nucleic acid into 
fragments, thus defending the bacterium against the attacker. The 2020 Nobel 
Prize in Chemistry was awarded to CRISPR-Cas pioneers Emmanuelle Charpentier and 
Jennifer Doudna, who developed the CRISPR-Cas system to precisely edit genomic 
DNA. This technology has exploded at a breathtaking pace and is now used by 
almost every molecular biology laboratory around the world in a myriad of 
organisms. In this Virtual Issue, the FEBS Journal features articles reviewing 
the development of CRISPR/Cas9 technology and its applications to understand the 
functions of proteins in vivo.