A cell holder is a laboratory apparatus used to hold a sample cell in place for spectroscopic analysis. The sample cell is typically a rectangular or cylindrical container that holds a liquid or gas sample for analysis, and the cell holder secures the sample cell in place and ensures that it is properly aligned with the spectrophotometer. Cell holders are typically made of metal or plastic and are designed to hold a specific size and shape of sample cell. They can be heated or cooled to control the temperature of the sample, and can be used with a variety of different spectrophotometers and other instruments. Cell holders are commonly used in chemistry, biology, and other scientific fields for applications such as measuring the concentration of a particular substance in a sample, or analyzing the properties of a particular chemical or biological system. They are available in a range of sizes and configurations, and can be adapted to suit different experimental setups and analytical techniques.