The present invention provides a method to cure material (polymer, metals) into a mold against the shape of a fluid (aka the substrate). The substrate is a ferrofluid, and its shape can be dictated by surrounding magnetic fields. By manipulating the applied magnetic fields, the ferrofluid can be formed into a specific shape; then, the curing material (in fluid or powder form) can be molded against that specific shape. The ferrofluid shape can further be changed during the curing step to impact the final shape. The methods of the present invention permit fast three-dimensional molding in a programmable fashion.