The mechanism of environmental intercrystallite crazing (EIC) of semicrystalline poly(tetrafluoroethylene) (PTFE) films was studied. Stress-induced cavitation and fibrillation upon the EIC process provides the development of a marked porosity in PTFE (up to similar to 40%) and pores with nanoscale dimensions (below 10 nm). Morphology and structural parameters of the mesoporous EIC PTFE samples were characterized, and the mechanism behind the EIC and low-temperature strain recovery of the EIC PTFE samples was proposed. The resultant mesoporous PTFE materials are shown to exhibit high chemical resistance, thermal stability, thermal conductivity, etc. The PTFE mesoporous materials can serve as matrices for diverse PTFE-based nanocomposite materials via the introduction and immobilization of various low-molecular-mass additives (alkali, metals, dyes). The bottom-up synthesis of silver nanoparticles within the mesoporous EIC PTFE as microreactors was described, and the structure of the silver-containing PTFE was characterized. Possible practical applications of the PTFE-based EIC nanomaterials were highlighted.