A method and apparatus wherein small, two- or three-dimensional structures are formed by multiple-photon-absorbed photopolymerization and/or cross-linking of a precursor composition, that is, photopolymerization using multi-photon excitation. Use of multi-photon excitation allows fabrication of structures and structural features having at least one dimension of less than about 1 micron, preferably less than about 500 nm, more preferably less than about 250 nm, and most preferably of less than about 100 nm, in bulk phase as well as in solution, and from a wide variety of organic and inorganic precursor subunits, including synthetic polymers and biological polymers such as proteins, lipids, oligonucleotides, and the like.