Conventional solid films on certain substrates play a crucial role in various applications, for example in flat panel displays, silicon technology, and protective coatings. Recently, tremendous attention has been directed toward the thinning and shaping of solids into so-called nanomembranes, offering a unique and fantastic platform for research in nanoscience and nanotechnology. In this Review, a conceptual description of nanomembranes is introduced and a series of examples demonstrate their great potential for future applications. The thinning of nanomembranes indeed offers another strategy to fabricate nanomaterials, which can be integrated onto a chip and exhibit valuable properties (e.g. giant persistent photoconductivity and thermoelectric property). Furthermore, the stretching of nanomembranes enables a macroscale route for tuning the physical properties of the membranes at the nanoscale. The process by which nanomembranes release from a substrate presents several approaches to shaping nanomembranes into three-dimensional architectures, such as rolled-up tubes, wrinkles, and the resulting channels, which can provide fascinating applications in electronics, mechanics, fluidics, and photonics. Nanomembranes as a new type of nanomaterial promise to be an attractive direction for nanoresearch.