The fine adjustment knob on a microscope is used to make small adjustments to the focus of the microscope to achieve optimal clarity and detail. It is typically located on the microscopes frame and works in tandem with the coarse adjustment knob. While the coarse adjustment knob facilitates initial focusing by rapidly moving the objective lens closer to or farther away from the specimen, the fine adjustment knob serves a more refined purpose. The fine focus knob is sometimes separate from the coarse focus knob, and sometimes it sits on top of the coarse focus knob. The fine adjustment knob is smaller in diameter than the coarse focus knob. When focusing on an object, you first use the coarse adjustment knob to bring the specimen into a rough focus range, and then use the fine adjustment knob to fine-tune the focus of the microscope to achieve optimal clarity and detail. The fine adjustment knob moves the stage or the body tube much slower than the coarse adjustment knob.