Perspectives on double-excitations in TDDFT

► We study double excitations in time-dependent density functional theory (TDDFT). ► We discuss why they are important for many of the current difficulties in TDDFT. ► A recent method for doubly-excited autoionizing resonances is tested on the He atom. ► We analyze what double excitations are present in the adiabatic quadratic response. ► We show how a semiclassical approach to correlation can yield double excitations.