Access to NC building blocks with precisely controlled size, shape, and composition, and advances in synthetic control over inter-NC coupling have created a fertile opportunity space to design materials particularly interesting for (opto-)electronic applications. The fabrication of epitaxially attached NC superlattices (SLs) on a fluid-fluid interface involves orchestrated translation and orientation of thousands of unconnected NCs. At first glance, this fabrication is rather simple; however, a number of sub-processes and their impact on the SL structure are not yet well understood. Understanding the mechanism and ultimately directing NC SL self-assembly and attachment has important implications on future advances in this emerging field. We fabricated NC SLs containing multiple stages of the SL transformation. We characterized these transient regions with 4D-STEM at single particle level using an electron microscope pixel array detector (EMPAD) and obtained a full description of the NCs crystallographic orientation. We discovered that the hexatic-to-square SL transformation is dominated by translation of pre-aligned NCs correlated along the <11n>AL direction and occurs stochastically within single SL domains. We used the detailed structure characterization obtained from the EMPAD to study the nucleation of NC attachment with molecular dynamics and found that dimer formation is inherent to the attachment mechanism. We present experimental evidence of dimer formation and rationalize the emergence of commonly observed SL defects, such as strain and missing bridges. Our work suggests that these defects are formed due to orientational and translational misalignment in dimers, which have less freedom to rotate and may get trapped in a less favorable (misaligned) states. We investigated the impact of NC size distribution on the local SL order, characterized grain boundaries, and proposed a mechanism for twin boundary formation. Finally, we studied the formation of thermally triggered 1D NC structures. We show that solvent evaporation can be used as a knob to control wire length and to potentially form more complex corrugated assemblies. Our work reveals rich insights into SL structure and transformation and provides a path forward toward the controlled fabrication of ordered SLs.