Developed HII regions (red circles numbered 1-7, Cao et al. 2019) and massive cores (red triangles) in Cygnus X. The background is the high-contrast column-density map (Cao et al. 2019). The cyan rectangles show four regions where filament ages were computed (Sect. 3.4 for details). The orange rectangle to the northwest shows evidence that filaments are compressed by the No.4 HII region (see also Sect. 3.4 for details). The majority of high-mass filaments and cores tend to be located on the boundaries of HII regions or the intersections of multiple HII regions, hinting at a strong relationship between the HII regions, filaments, and high-mass cores.