where formula_68 is the size of the contact region between the indenter and the sample, and formula_71 is the sample’s elastic modulus. Typical atomic-force microscopy (AFM) cantilevers have formula_63 in the range 0.05 to 50 N/m, and probe size in the range ~10 nm to 1 μm. Commercial nanoindenters are also similar. Therefore, if formula_63≈formula_64, then a typical AFM cantilever-tip or a commercial nanoindenter can only measure formula_69 in the ~kPa to GPa range. This range is wide enough to cover most synthetic materials including polymers, metals and ceramics, as well as a large variety of biological materials including tissues and adherent cells. However, there may be softer materials with moduli in the Pa range, such as floating cells, and these cannot be measured by an AFM or a commercial nanoindenter.