He had two passions growing up: following his hometown soccer team Club Atlético Newell's Old Boys, and reading about science.

He earned a PhD from the University of Chicago investigating the biochemistry and biological role of sortase, a transpeptidase that links surface proteins to the envelope of Gram-positive bacteria, in the laboratory of Dr. Olaf Schneewind.

[4][5][6] In 2008, Marraffini joined the laboratory of Dr. Erik Sontheimer at Northwestern University as a Jane Coffin Childs Memorial Fund for Medical Research Fellow.

[7] This study was key to understand the mechanisms of CRISPR immunity at the molecular level and also predicted the existence of RNA-programmable Cas nucleases and their current applications to gene editing.

[8] In 2012, he initiated a collaboration with Dr. Feng Zhang of the Broad Institute of MIT and Harvard that culminated in the development of the revolutionary CRISPR-Cas9 technologies to edit the genomes of bacteria and human cells.