This article profiles the work of Elise Knittle, whose research specialty is mineral physics. The essay gives an overview of the core, mantle, and crust of the Earth, including what we know about their physical properties. It explains the work of the author, studying the chemical interactions between the metals that make up the Earth’s core and the silicate minerals that compose the mantle. The obstacles and challenges she faces in re-creating the intense heat and pressure of the deep Earth using incredibly small samples are explained. Most of the recent work of the author is on subduction zones, trying to determine what happens to the slabs of oceanic crust that descend into the mantle.