 Optical microscopy allows us to see small objects by magnifying light through a series of lenses. Compound microscopes have been used since the 17th century and have led to numerous discoveries in cellular biology and other fields of science. Material scientists use optical microscopy to investigate material properties such as grain size or fracture features. This video will demonstrate the basic operation of the Olympus Optical Microscope. The sample is placed onto the sample stage underneath the objective lens. The sample stage can be adjusted in the Z direction by turning the outer knob and finally adjusted by turning the inner knob. These adjustments are used to put the sample into focus. The X and Y axes of the sample stage can be moved by turning the knob on the side of the sample stage. Light intensity can be adjusted. The light source can be switched between above or below the sample. The light source can be switched between bright field and dark field to change how light enters the objective lens. The image of the sample can be viewed through the ocular lenses, the camera, or both, and can be switched by pulling out or pushing in the rod on the side of the microscope head. When viewing through the ocular lenses, it should not be necessary to place your eyes on the eye pieces. The user should start with the lowest magnification objective lens. The sample stage is adjusted in the Z direction to focus the image. The revolving nose piece is turned to the next objective lens to increase the magnification. The Z axis may have to be readjusted to focus the sample. Make sure there is enough clearance between the sample and objective lens before turning. A live image can be started by clicking the live button. To take an image, the snap button is pressed. When switching between objective lenses, the user must manually change the scale bar by selecting the objective lens button accordingly. To save the image, right-click on its tab and click Save. To embed the scale bar in the saved image, it must be saved as a JPEG type file. This microscope has a pair of polarizing plates, one of which is rotatable. One plate polarizes the source light from above the sample, and the other polarizes the reflected light being viewed. Polarized light can be used to identify different phases of material or internal stress. To apply polarization, the polarizing plates are pushed in until they are latched into place. This example uses mica to demonstrate polarization. Mica is a naturally occurring layered birefringent material. With the polarizing plates pushed in, polarized light is reflected off the mica, which changes the phase of the polarized light. When the light passes through the second cross-polarizer, only part of the reflected light is transmitted. This results in different thicknesses of mica to produce different colored light, which changes color when the cross-polarizer is rotated. When finished, the user should change the objective lens to its smallest magnification, reduce light intensity, and turn off the power. Then place the dust cover over the microscope.