The nosepiece on a microscope is a circular structure that holds the objective lenses and attaches them to the microscope head. It is also called the turret and can be rotated to change which objective lens is active. The objective lenses are the lenses closest to the specimen and are responsible for magnifying the image. To change the magnification power, simply rotate the turret. The nosepiece is an important part of the microscope because it allows the user to switch between different objective lenses and achieve various levels of magnification. Without the nosepiece, the microscope would only provide one level of magnification.