Short answer: like magic! Absorption is what happens when a sponge soaks up urine. The urine remains in the sponge unchanged, and the odor still emanates from the sponge, just as occurs with other cat litters. Adsorption is a chemical interaction whereby a change of physical properties occurs. The crystals contain millions of microscopic pores that exhale moisture. Silica sand crystals adsorb urine and its odor until a saturation point occurs, at which time the litter should be changed. This adsorption process also kills bacteria.