Hormesis is the term that describes any process in a cell or organism that exhibits a biphasic response to exposure to increasing amounts of a substance or condition. Within the hormetic zone there is generally a favorable biological responses to low exposures to toxins and other stressors. Hormesis comes from Greek hórmēsis "rapid motion, eagerness", itself from ancient Greek hormáein "to set in motion, impel, urge on". A pollutant or toxin showing hormesis thus has the opposite effect in small doses as in large doses. Hormetics is the term proposed for the study and science of hormesis. A related concept is Mithridatism, which refers to the willful exposure to toxins in an attempt to develop immunity against them.