Size selective self-sorting in the coordination-driven self-assembly of two-dimensional (2-D) polygons and three-dimensional (3-D) cages is presented. Two types of polygons (rectangular and triangular) of different size are formed spontaneously from within mixtures of a molecular "clip" or a 60 degrees organoplatinum acceptor with dipyridyl linkers of different lengths via self-sorting. Furthermore, two different sized 3-D supramolecular cages are formed upon mixing one ditopic organoplatinum acceptor and two different sized tritopic donors from the self-sorting process. The formation of these polygons and cages is characterized using NMR spectroscopy and electrospray ionization mass spectrometry (ESI-MS). In all cases, the self-sorting process is directed by the size of the donor building blocks and a dynamic, thermodynamically driven self-correction process resulting in the formation of discrete products from complex mixtures.