The present disclosure describes kits and compositions for three dimensional printing, systems for three-dimensional printing, and methods of making three-dimensional printed articles. In one example, a multi-fluid kit for three-dimensional printing comprises: a fusing agent comprising water and a radiation absorber, wherein the radiation absorber absorbs radiation energy and converts the radiation energy to heat; and a pore-promoting agent comprising water and a water-soluble pore-promoting compound, wherein the pore promoting compound chemically reacts at an elevated temperature to generate a gas, and wherein the water-soluble pore-promoting compound is selected from the group consisting of sodium bicarbonate, potassium bicarbonate, and combinations thereof.