 Rechargeable batteries are everywhere. They're in our homes, in our cars, and even in our pockets. Even as battery technology has matured, however, the physical and chemical processes that unfold inside of a battery as it delivers power have remained largely hidden from view. But thanks to advancements in electron microscopy and methods for handling materials on the nanoscale, scientists and engineers now have front-row seats to the action. Over the past decade, tremendous progress has been made to push the resolution of the Transmission Electron Microscope, or TEM, to smaller and smaller scales. As a result, scientists can now routinely image individual atoms in many materials. But it takes more than high resolution to catch a glimpse of what goes on inside of a battery while it is operating. One of the biggest problems is size. Even the smallest coin-shaped batteries found in cameras and toys are too big to view under an electron microscope, and even if they could fit, slicing them open would necessarily compromise their function. To address these problems, scientists and engineers have devised various ways of miniaturizing rechargeable batteries and making their key components visible under a TEM, all while preserving battery function. Collectively referred to as in C2 TEM, these techniques are helping researchers tackle some of the biggest questions in battery research. What causes rechargeable batteries to fail? How do the various electrochemical components of a battery interact? How can batteries be made better? The simplest design features a single nanowire as the working electrode, an ionic liquid or lithium oxide as the electrolyte, and a lithium-based metal oxide as the counter electrode. With such small active components, the open-cell configuration can be easily integrated into the small grids used to hold TEM samples and can be assembled relatively quickly. And in addition to supporting atomic-level imaging, this configuration allows scientists to study how lithium ions are shuttled into and out of the electrodes as a battery is charged and discharged. But while the structural response of the electrode materials adequately simulates what goes on in a real battery, this open-cell layout mainly serves as a simple model of the much more complex structure of rechargeable batteries. The design is therefore limited in many ways, one of the most important being the limited contact between the electrolyte and the electrodes. To address this shortcoming, scientists can assemble a closed-cell configuration in which both electrodes are bathed in a liquid electrolyte. A typical cell of this type features the electrodes and electrolyte encased in layers of silicon to create the sandwich-like structure commonly found in computer chips. A silicon nitride window at the center of the chip allows an electron beam to go through and capture lithium transport in action as the battery is charged and discharged. This type of cell has allowed scientists to better understand one fundamental battery process in particular, the formation of the solid electrolyte interface. This layer between the electrolyte and the electrode plays a major role in how lithium ions move into and out of an electrode and ultimately affect battery life and performance. Despite providing an unprecedented new look at the behavior of rechargeable batteries, the current state of in-situ TEM for battery research is still limited. As researchers look to improve these techniques, they must account for the effects of the electron beam on the electrolyte, the less-than-optimal image resolution that can be achieved through liquid electrolytes, and, most importantly, the limited number of times cells can be charged and discharged under a microscope.