Rechargeable Lithium ion batteries (LIBs) are commonly used power source in everyday electrical devices. Understanding the real-time atomistic evolution of the electrodes in a LIB is indispensable since the performance of a LIB is governed by electrochemical reactions and possible mechanical degradation of the electrodes during the operation of a battery. With advances in high resolution transmission electron microscopy and microfabrication techniques, it has been possible to investigate the evolution of solid electrolyte interphase, electrolyte decomposition, and the response of the electrode upon lithiation-delithiation at the atomic scale. This article provides a comprehensive review of the current understanding of lithiation-delithiation mechanisms in LIBs.