The INTernational Gamma-Ray Astrophysics Laboratory (INTEGRAL) has been crucial in our understanding of astrophysical phenomena over a wide energy and temporal range. Its unique capabilities in terms of combined sensitivity, energy coverage, energy resolution, and sky coverage at once, led to the discovery of many classes of previously unknown astrophysical objects and the elucidation of poorly understood transient celestial sources. The mission's long life has allowed for very long observations that have permitted the detection of elusive signals from faint gamma-ray line emissions, a unique INTEGRAL asset. The availability of telemetry on ground within seconds from photon detection together with the high duty cycle have permitted the discovery and characterization of rare transient events, which have made INTEGRAL a cornerstone in the new era of time-domain and multi-messenger astronomy. This has fostered collaborations and synergies with current and future missions that will enhance INTEGRAL's legacy of twenty-two years of publicly available science data that will continue to provide a wealth of scientific information to be explored in supporting new questions, new missions, and new perspectives on astrophysical phenomena.