The crystallization process of high (HMF), medium (MMF) and low (LMF) melting fractions of milk fat and their mixtures was studied at 5, 15, and 25°C. Solid fat content (SFC) was measured by pulsed nuclear magnetic resonance, melting behavior was characterized by differential scanning calorimetry, and polymorphism was studied by synchrotron x-ray diffraction. The microstructure was imaged by polarized light microscopy and fractal dimensions of the crystal networks were calculated from the micrographs by a box counting method. HMF was responsible for nucleation and the initial stage of crystal growth at all temperatures studied. MMF displayed an ambivalent behavior (i.e., as a high and low melting fraction) depending on the proportion at which it is present and the crystallization temperature. The presence of MMF and/or LMF resulted in a decrease of SFC, and the induction of a two-step crystallization due to secondary crystallization and polymorphic transformations. The morphology of the crystals, the formation of a fat network as well as the nucleation and growth mechanism were dictated by the composition of the mixtures and temperature of crystallization.