Control samples are used in scientific experiments to provide a reference point for comparison. They are typically taken from the same population as the experimental group, but they do not receive any treatment or intervention. This allows researchers to compare the results obtained from the control sample with those of the treated group and determine if there is a statistically significant difference between them. Control samples help ensure that any observed changes in the experimental group are due to the specific treatment being tested rather than other factors, such as natural variability or random chance.