Stereology is the method of sampling and counting material utilising particular protocols to get an estimate of a quantitative parameter, such as number, length, volume, etc. Getting accurate measures is a significant component of producing a study result with statistical validity. By utilising proper sampling procedures and using counting or mapping protocols (known as probes), stereology makes it feasible to avoid potential artefacts and errors that could significantly skew outcomes. When correctly applied, stereology can allow for constant detection of differences only slightly bigger than inter animal variation. As changes of physiologically related ranges within the tissue are usually far below a fold variation, stereology gives a strong analytical tool for in vivo histological studies. It can often be used in vitro studies to increase sampling validity for quantitative parameters. This innovative design-based stereology has almost entirely supplanted the application of the older geometric model-based stereology in most biological analysis purposes.