“…The rapid emergence of next-generation X-ray sources, including near diffraction-limited storage rings (DLSRs) such as PETRA IV (Schroer et al, 2018), MAX IV (Bjo ¨rklund Svensson et al, 2019), ESRF-EBS (Chenevier & Joly, 2018) and APS-U (Dooling et al, 2022), as well as free-electron lasers (FELs) such as European XFEL (Tschentscher et al, 2017), LCLS II (Halavanau et al, 2019), SwissFEL (Milne et al, 2017) and SACLA (Yabashi et al, 2017), promises an increase of coherent X-ray flux by several orders of magnitude. Combined with the development of high-speed, highfidelity pixelated photon-counting X-ray detectors (Pennicard et al, 2018;Allahgholi et al, 2019;Ballabriga et al, 2018;Mo ¨ller et al, 2019), XPCS will have the potential to fill the 'noman's land' in S(Q, !)…”