An optically heterogeneous phantom structure for use in optical imaging techniques. The phantom structure includes an external shape simulating an object to be subjected to an optical imaging technique, the external shape defining an external surface that encloses an internal volume of the external shape and an optically heterogeneous material filling the internal volume and having heterogeneous optical properties for simulating at least one optical parameter of at least one region within the object. A method of producing the optically heterogeneous phantom structure. The method includes selectively depositing precursors of a first material and a second material by 3D printing so that the precursor of the second material is surrounded by the precursor of the first material within a predetermined internal region of the precursor of the first material, and forming the phantom structure. Variations of the method include additives to the materials.
