One building block is placed on top of another one, an atom of sodium combines with an atom of chlorine. Do new things result in each case? Or, to put it more generally, under what conditions do various parts form a material object, i.e. a substance? Hubner addresses the problem by developing separate analyses for the composition of masses, bodies, artefacts and living organisms. The first main line of argument develops analyses for the species named above and discusses their existence against the touchstone of classic puzzles, such as that of the ship of Theseus. The second main line of argument starts from the discussions of four-dimensionalism and the problem of vagueness to reject the views that the formation of complex structures under any particular conditions is either given or not given. Hubner introduces a current international debate to German readers.