The Slotkin laboratory uses Arabidopsis thaliana, a reference flowering plant, as a model to investigate how eukaryotic cells repress transposable elements. Transposable elements are fragments of DNA that can duplicate or move from one location to another. Their ability to replicate has resulted in transposable elements occupying vast amounts of most eukaryotic genomes, including nearly half of the human genome. Although often overlooked or dismissed as “junk DNA”, transposable elements have played an important role in the structure and evolution of the eukaryotic genome. However, when transposable elements are active, they cause DNA damage and new mutations by inserting into essential protein-coding genes or by promoting rearrangements and genome instability.