The chapter discusses the nuclear activity in nearby galaxies, focusing on low-luminosity active galactic nuclei (LLAGNs) and their implications for black hole demographics and accretion physics. It highlights that a significant fraction of nearby galaxies exhibit weak nuclear activity, primarily due to black hole accretion with low rates. This activity often results in modifications to the central engine, such as the disappearance of the broad-line region and obscuring torus in faint sources, and the transformation of the optically thick accretion disk into a three-component structure. The review emphasizes that most, if not all, bulges host central supermassive black holes, but the presence of active nuclei in late-type galaxies suggests that a classical bulge is not a prerequisite for a central black hole. The chapter also covers spectral classification methods, surveys of nearby galactic nuclei, host galaxy properties, and the implications of LLAGNs for understanding black hole demographics and accretion physics. It concludes by discussing the challenges and future directions in studying nuclear activity in nearby galaxies.The chapter discusses the nuclear activity in nearby galaxies, focusing on low-luminosity active galactic nuclei (LLAGNs) and their implications for black hole demographics and accretion physics. It highlights that a significant fraction of nearby galaxies exhibit weak nuclear activity, primarily due to black hole accretion with low rates. This activity often results in modifications to the central engine, such as the disappearance of the broad-line region and obscuring torus in faint sources, and the transformation of the optically thick accretion disk into a three-component structure. The review emphasizes that most, if not all, bulges host central supermassive black holes, but the presence of active nuclei in late-type galaxies suggests that a classical bulge is not a prerequisite for a central black hole. The chapter also covers spectral classification methods, surveys of nearby galactic nuclei, host galaxy properties, and the implications of LLAGNs for understanding black hole demographics and accretion physics. It concludes by discussing the challenges and future directions in studying nuclear activity in nearby galaxies.