Micronuclei are one or rarely multiple supernumerary nuclear structures often observed
as a result of xenobiotic treatment within the cytoplasm of an erythrocyte having the following characteristics: a distinct outline to the structure, a round, almond or ovoid
shape, a diameter 1-1 th of the erythrocyte, staining characteristics consistent with chromatin of the main nucleus, either dissociated from or connected to the main nucleus by a very thin basophilic strand.