Optical imaging with high spatiotemporal resolution and analytical accuracy is becoming the mainstay of tools capable of deciphering molecular dynamics and activities in single living cells. Over the past decades, information obtained by optical imaging has greatly enriched and reshaped our knowledge of biology and medicine. Investigating epigenetic modifications by optical microscopy and spectroscopy is expected to be the wave of the future or might even become the norm to complement biomedical practice. Independent of classical genetic mechanisms, epigenetics has recently drawn substantial attention due to its extensive involvement in physiological and pathological processes, as well as its reversibility. In order to understand the real-time behaviors of epigenetic regulation, nanoscale inspection at the sub-second timescale is imperative. In this chapter we discuss the basics of state-of-the-art optical methods for life science research and their potential applications in imaging live-cell epigenetics. Moreover, with established experience in single-molecule detection, we provide practical guidance on how to choose and adapt optical instrumenta-tions for different applications. Last, recent advancements and representative examples in sensing live-cell epigenetics are reviewed.