The present disclosure relates to a three-dimensional (3D) printing materials kit comprising: a first tailoring agent comprising at least one crosslinking agent; a second tailoring agent comprising at least one plasticizer, and a fusing agent. The present disclosure also relates to a printed structure comprising regions of relatively higher ductility and regions of relatively lower ductility. The regions of relatively higher ductility can be interspersed by the regions of relatively lower ductility, and the regions of relatively lower ductility can be formed from a crosslinked polymer and/or a polymer composition comprising a reinforcing filler, and/or the regions of relatively higher ductility can be formed from a polymer composition comprising a plasticizer. The present disclosure also relates to a method of three dimensional printing (3D) that can be used to print a 3D printed object comprising the printed structure described above.