Electron microscopes use electron lenses to focus the beam of electrons onto the sample. There are several types of electron lenses that are used in electron microscopes, including: 1. Electromagnetic lenses: Electromagnetic lenses are used in transmission electron microscopes (TEMs) to focus the beam of electrons onto the sample. They consist of a series of electromagnets that bend the path of the electrons and can be used to adjust the focus of the beam. 2. Electrostatic lenses: Electrostatic lenses are used in scanning electron microscopes (SEMs) to focus the beam of electrons onto the sample. They consist of a series of electrostatic plates that are charged to different potentials, which deflect the electrons and focus them onto the sample. 3. Hybrid lenses: Hybrid lenses are a combination of electromagnetic and electrostatic lenses and are used in some types of electron microscopes to focus the beam of electrons onto the sample. Hybrid lenses offer the benefits of both electromagnetic and electrostatic lenses and can be used to achieve a high-resolution image. In addition to these types of lenses, electron microscopes may also use other types of lenses, such as aberration correctors and condenser lenses, to adjust the focus and contrast of the beam of electrons.