A microscope is an instrument used to see objects that are too small for the naked eye. The science of investigating small objects using such an instrument is called microscopy. Optical microscopes consist of a lens or combination of lenses. Others, such as the electron microscope, use other means of magnification, such as beams of electrons. A Simple microscope is a microscope that uses only one lens for magnification. The electron microscope is a type of microscope that uses a beam of electrons to create an image of the specimen. A phase-contrast microscope utilizes the phase differences of light rays transmitted by different portions of an object to create an image in which the details of the object are distinct despite their near uniformity of refractive index.