In an example of a three-dimensional (3D) printing method, a polymeric or polymeric composite build material is applied. A fusing agent is selectively applied on at least a portion of the polymeric or polymeric composite build material. The fusing agent includes a discolorable near-infrared absorbing dye, a thiol surfactant, a reducing agent, and a balance of water. Near-infrared radiation is applied to the polymeric or polymeric composite build material at a condition that maintains a temperature of the selectively applied fusing agent below a decomposition temperature of the fusing agent and that allows the discolorable near-infrared absorbing dye to harvest near-infrared radiation energy, in order to fuse the portion of the polymeric or polymeric composite build material in contact with the fusing agent to form a layer and to initiate discoloration of the discolorable near-infrared absorbing dye in the layer.