Liquid-liquid phase separation (LLPS) is a process through which a homogeneous phase separates into two or multiple phases. This process is observed in systems spanning biology and synthetic polymeric systems. The distinct phases have direct influence on things like material properties, morphology, and material interactions with other interfaces. In my research, I explore how phase separated droplets influence self-assembled polymer morphologies in solution and on solid substrates. I used techniques like cryogenic electron microscopy (cryo-EM), liquid phase electron microscopy (LP-EM), and optical microscopy to study my systems. I developed the first example of nonionic block copolymer coacervates and demonstrated how the coacervates encode morphological information towards the solid phase self-assembly. Using LPEM, I showed block copolymer coacervates are also intermediates during supported bilayer formation. This new mechanism of bilayer assembly should be beneficial for forming pristine supported bilayers. Additionally, I discovered the auto-confining effects within the phase separated droplets were shown to favor complex block copolymer morphologies that are usually accessed by inducing confinement of block copolymers in emulsions. Furthermore, I developed a model block copolymer system in which LLPS occurs during light-induced polymerization mimicking active biological processes. Lastly, I developed a workflow to image phase separated droplets of polymers or proteins using cryo-EM which enabled 2D and 3D nanoscale characterization. The collection of this work informs how phase separated droplets behave and influence block copolymer self-assembly.