Engineered photonic nanostructures offer the exciting potential to create customized nonlinear optical media with tailored high-order effects, which are essential to the active control of light and the generation of new spectral components. Leveraging the electrical and optical functions simultaneously supported in certain nanophotonic systems, we can realize externally triggered and dynamically controllable light-matter interactions for nonlinear optical generation and signal processing. In particular, we harness the transient disruption of the inversion symmetry for second-order optical processes, and facilitate the hot-carrier-induced perturbation of the dielectric permittivity for all-optical control of light. Such effects are exploited in a variety of nanophotonic platforms, including plasmonic structures, dielectric metasurfaces, and two-dimensional crystals. Our studies reveal a grand opportunity to exploit photonic nanostructures as self-contained platforms with intrinsically embedded electrical functionality and optical nonlinearity, and conversely, to elucidate the dynamics of carrier generation and transport via nonlinear optical means.