Regulation – and deregulation – of gene expression are critical events for every process within the cell. Alteration of these intricate processes, for example as consequences of genetic defects or bacterial/viral infections, can readily lead to one of many human ailments. The control of these processes is commonly modulated by multi-protein complexes; in fact, proteins rarely act alone, but interact intimately and precisely with other proteins and nucleic acids to properly perform their cellular functions. My laboratory studies the structure and molecular mechanisms of macromolecular machines involved in DNA maintenance and RNA maturation and biogenesis. We use cryo-electron microscopy and single particle reconstruction techniques as a primary tool for visualizing these complexes and, thus, to better understand their functions.