Authors: Sangmin Lee, Erin G. Teich, Michael Engel, and Sharon C. Glotzer Complex crystallization pathways occur in a variety of systems both in nature and in simulations and experiments. These systems transition from the fluid phase to the solid phase, not via classical nucleation and growth, but rather through the emergence of single or multiple structural precursors in the fluid, which then give rise to the crystallization of the solid phase. The influence of these precursors on the solid phase crystallization, and the structural characteristics of the prenucleation phases, have yet to be fully elucidated. Here, we report three instances of two-step crystallization of hard-particle fluids, in which crystallization proceeds via a high-density precursor fluid phase with prenucleation motifs in the form of clusters, fibers and layers, and networks, respectively. These are motifs of varying dimension and complexity. We explore the influence that the dimension of these prenucleation motifs has on the crystallization process, and we structurally and dynamically characterize each crystallization event. The crystals that form are complex, including, notably, a crystal with 432 particles in its cubic unit cell. Our results establish the existence of two-step crystallization pathways in entropic systems and showcase the accompanying variety of prenucleation structures that are possible.