Dynamic light scattering (DLS) is a technique used to measure the size of small particles in a liquid. It works by shining a laser light on a sample, which causes the particles to scatter the light. As the particles move, the scattered light fluctuates in intensity, and these fluctuations can be analyzed to determine the size and distribution of the particles. DLS is commonly used in various fields, including biotechnology, pharmaceuticals, and materials science. It is particularly useful for studying nanoparticles and colloids, providing insights into their stability and behavior in different environments.