Colony Forming Units (CFU) refers to the number of viable bacteria or fungi in a sample that can multiply and form colonies. This measurement is crucial in microbiology for estimating the number of living microorganisms present. CFU is determined by spreading a diluted sample across a petri plate and counting the resulting colonies. Each colony is assumed to have grown from a single CFU, which could be one cell or a group of cells. This method counts only the viable cells capable of replication, unlike microscopic examination, which counts all cells, living or dead. The count is expressed as CFU per milliliter (CFU/mL) or CFU per gram (CFU/g), depending on the sample’s state. It’s important to note that the actual number of cells can be higher than the CFU count, as some cells may clump together or grow in chains, leading to undercounting.