Abstract: The present invention relates to methods and apparatuses involving biocompatible structures for tissue engineering and organ replacement and, more specifically, to methods and apparatuses involving biocompatible structures formed by three-dimensional fabrication for tissue engineering and organ replacement. In some embodiments, the biocompatible structures are scaffolds for cells that can be used as tissue engineering templates and/or as artificial organs. The structures may be three-dimensional and can mimic the shapes and dimensions of tissues and/or organs, including the microarchitecture and porosities of the tissues and organs. In some cases, a structure formed by three-dimensional fabrication comprises a wall defining a cavity and a plurality of pores in at least a portion of the wall. The pores may permeate the wall and enable exchange of a component (e.g., a molecule and/or a cell) between a portion interior to the cavity and a portion exterior to the cavity.