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| 20th century || The first electron microscope is invented by {{w|Max Knoll}} and {{w|Ernst Ruska}}, blasting past the optical limitations of the light. By the late 1930s, electron microscopes with theoretical resolutions of 10 nm are designed and produced.<ref name="Overview of Electron Microscopy">{{cite web |last1=Palucka |first1=Tim |title=Overview of Electron Microscopy |url=https://authors.library.caltech.edu/5456/1/hrst.mit.edu/hrs/materials/public/ElectronMicroscope/EM_HistOverview.htm |website=caltech.edu |accessdate=30 January 2019}}</ref> The second major development for microscopes in the 20th century is the evolution of the mass market.<ref name="History of Microscopes"/> The 1960s through the 1990s produce many innovative instruments and trends on electron microscopy.<ref name="Overview of Electron Microscopy"/> In the 1970s, sufficient information on ultrastructural pathology becomes accumulated to allow the use of the {{w|electron microscope}} as a diagnostic tool.<ref name="Immunohistology and Electron Microscopy of Anaplastic and Pleomorphic Tumors"/>

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