I-diffusion eyenzeka ngokweenkqubo ezimbini: e-chemical ne-biological, ii- molecules zihamba zingumthombo zisuka kwinto okanye kwindawo ethile , esingathi (ngamanye amagama apho kuqhuma khona) yi-high concentration (apho zininzi khona ezi- molecules) zisiya kwindawo echazwa ngokuba i-low concentration (apho ke zimbalwa khona ezi molecules).