Conversion of CO2 and CH4 into syngas offers a promising route to reduce emissions of greenhouse gases, which facilitates large‐scale carbon fixation and boosts carbon‐neutral goal. The main obstacle for CO2/CH4 reforming is the lack of durable catalysts showing both high metal‐exposure and high‐temperature structure stability, since the reported Ni‐based catalysts have difficulty in avoiding deactivation by sintering metal at high temperature. Herein, ultra‐small Ni nanoparticles, which display multiple characteristics of high surface‐exposure and stabilized structure, are constructed from the evolution of atomically dispersed low‐valent nickel under a dually confined microenvironment. Consequently, the developed strategy can not only break the stable‐exposure trade‐off in heterogeneous catalysis but also provide new opportunity for the engineering of high‐performance and sintering‐resistant reforming catalysts as well as other durable heterogeneous catalysts.