Studies have been conducted on the kinetics and morphology of dendrite formation in model systems over a range of supercoolings. The evolution of microstructure from the nascent dendritic state can be quantified through a series of scaling laws based on such fundamental considerations as heat and solute transport and interfacial dynamics. A brief review is presented of the salient ideas that explain dendrite formation as an interfacial stability. The influence of parameters of the materials on the microstructures of aluminum alloys versus those of the experimentally studied model systems will be discussed, along with the effects of certain processing parameters such as supercooling, supersaturation, or cooling rate. The key requirements for suitable organic models of aluminum solidifcation are that they possess cubic centrosymmetry (face-centered cubic or body-centered cubic), relatively low surface energy anisotropy, and molecularly rough solid/liquid interfaces to avoid facet formation and large departures from local equilibrium. The major microstructural relationships developed from our studies show that the initial branching, which eventually establishes the scale of microsegregation, is simply a multiple of the dendrite tip radius, which, in turn, depends on the local cooling rate and on certain groupings of the thermophysical constants.