The Cover Feature shows the Great Wall and ethylbenzene oxidative dehydrogenation reactions on carbon nanotube catalysts. The best view of the Great Wall can only been gained on top of the mountain after getting through each Beacon Tower. In their Communication, C. Wang, W. Liu et al. demonstrate that, just like touring the Great Wall, the reaction mechanism for nanocarbon catalyzed alkane oxidative dehydrogenations can be revealed via a series of in situ experimental strategies, including active site titration, kinetic analysis, isotope effect and surface reaction of a single reactant. More information can be found in the Communication by C. Wang, W. Liu et al. on page 397 in Issue 1, 2019 (DOI: 10.1002/cctc.201801547).