Contemporary transmission electron microscopes have resolutions down to 1.5--2 $\mathring{\mathrm{A}}$, and this enables one to observe atoms directly. A theory is presented of the formation of electronmicroscope images at atomic resolution, the influence of aberrations, the properties of the transfer function, and the methods of processing, calculating, and interpreting images. The relation is examined between electron microscopy and electron diffraction. Examples are given of electron-microscope studies of the atomic structure of various objects--molecules, crystals, various organic and inorganic compounds, including minerals and semiconductors, and of studies of defects of crystal-structure and of its formation during crystal growth.