Strain can be measured at the micron scale by Raman spectroscopy and X‐ray diffraction, but at the nanoscale, the only viable tool is transmission electron microscopy (TEM). TEM techniques can be divided into two categories: diffraction based techniques such as convergent‐beam‐electron‐diffraction or nanobeam electron diffraction, and imaged based techniques such as high‐resolution electron microscopy or the new technique of dark‐field electron holography (HoloDark). The latter has recently been invented to measure strain to high precision (2 × 10−4), nanometer spatial resolution, and for micron fields of view. In this article, we present two latest and typical results from the HoloDark technique (which is applicable to all standard focused‐ion beam prepared crystalline samples): mapping of strain in contact etch stop layers induced strain structures, and in implanted layers, In such materials and structures, the Holodark technique, although still perfectible, has no competitor.