A Colony Forming Unit (CFU) is a measure used in microbiology to estimate the number of viable bacteria or fungal cells in a sample. It represents a single cell or group of cells that can grow into a visible colony on a solid growth medium. CFUs are essential for quantifying microbial populations in various environments, such as soil, water, and clinical samples. In laboratory settings, researchers often use CFUs to assess the effectiveness of antimicrobial treatments or to study microbial growth patterns. By counting the number of colonies formed after incubation, scientists can determine the concentration of microorganisms in the original sample, aiding in various fields like medicine, food safety, and environmental science.