The self-assembly is based on "the thermodynamic tendency of multiphase liquid–liquid systems
to minimize their contact surfaces", the most awesomely complicated way of saying "oil and water don't mix" possible. By preparing polyethylene microgel components and adding them to an oil/water mixture, the specially shaped bits align themselves along the spherical liquid interfaces. Applying a few seconds of UV light fixes the microgel in position and you have a ready made, biocompatible (and degradable) matrix ready for the addition of cells.

Replicating the different tissue organizations of different organs becomes nothing more than a recipe book, choosing your initial microcomponents, mixture and baking time.