Spatiotemporal optical wavepackets refer to light fields with sophisticated structures in both space and time. The ability to produce such spatiotemporally structured optical wavepackets on demand attracted rapidly increasing interest as it may unravel a variety of fundamental physical effects and applications. Traditionally, pulsed laser fields are treated as spatiotemporally separable waveform solutions to Maxwell’s equations. Recently, more generalized spatiotemporally non-separable solutions have gained attention due to their remarkable properties. This review aims to provide essential insights into sculpting light in the space–time domain to create customized spatiotemporal structures and highlights the recent advances in the generation, manipulation, and characterization of increasingly complex spatiotemporal wavepackets. These spatiotemporally non-separable light fields with diverse geometric and topological structures exhibit unique physical properties during propagation, focusing, and light–matter interactions. Various novel results and their broad potential applications as well as an outlook for future trends and challenges in this field are presented.