Compositions and methods for 3D printing are described herein. In an example, a composition for 3D printing can comprise a build material comprising at least one polymer and at least one first electron donor compound; and a fusing agent comprising (i) a metal bis(dithiolene) complex, (ii) at least one surfactant, at least one second electron donor compound, or combinations thereof, (iii) a polar aprotic solvent, and (iv) water. The at least one first electron donor compound and the at least one second electron donor compound can be the same or different.