This part of ISO 14577 specifies a method for testing layers that is particularly suitable for testing thin layers in the nano or micro range. However, the application of the method from this part of ISO 14577 is not necessary if the penetration depth makes up such a small proportion of the layer thickness that the influence of the substrate can be neglected in every possible case and the layer can be regarded as a solid material. The limits for these cases are given. This test method is limited to the testing of individual layers if the indentation is perpendicular to the surface of the test specimen; however, graded layers or layers made up of several layers can also be measured in cross-section, if the thickness of the individual layers or the steps is greater than the spatial resolution of the penetration process. The test method is not limited to any particular type of material. The scope of this part of ISO 14577 includes metallic and non-metallic layers. In this part of ISO 14577, the term layer refers to any solid layer with homogeneous properties different from those of the substrate to which it is attached. The method assumes that the properties of the layer are independent of the depth of penetration. Composite layers are considered homogeneous if the structure size is smaller than the size of the indentation. The application of this part of ISO 14577 with regard to hardness measurement is only possible if when the indenter is a pyramid or a cone with a tip fillet radius small enough for plastic deformation to occur in the layer. The hardness of viscoelastic materials or materials that have significant creep is significantly affected by the duration of the test.