This article describes a complete study of the evolution of composition (from binary to quaternary) and shape (0D-1D) during the synthesis of CZTS nanocrystals. Aliquot studies were used to track the nucleation and growth in the early stages. Distinctive stages are evident in the reaction due to the progressive incorporation of tin and zinc into the primary copper sulfide particles as a result of their differing precursor reactivity. In addition, reaction windows for shape control were devised by tuning the amine concentration, thereby allowing the formation of a diverse range of shape morphologies including nanorods and ellipsoids, as well as atypical tadpole-shaped and P-shaped nanocrystals. Polytypic nanocrystals with wurtzite and zinc blende domains were also achieved by changing the type of metal precursors used initially in the reaction.