3D structures are written and developed in a crosslinked polymer initially formed by a DielsAlder reaction. Unlike conventional liquid resists, small features cannot sediment, as the reversible crosslinks function as a support, and the modulus of the material is in the MPa range at room temperature. The support structure, however, can be easily removed by heating the material, and depolymerizing the polymer into a mixture of low-viscosity monomers. Complex shapes are written into the polymer network using two-photon techniques to spatially control the photoinitiation and subsequent thiolene reaction to selectively convert the DielsAlder adducts into irreversible crosslinks.