Critical phenomena of a polymer solution or blend is an interesting topic for researchers to study extensively theoretically and experimentally for many decades. Polymer phase separation has a morphology of dot, line or bi-continuous shape. Application of this phase separation morphology is used for many potential applications such as photovoltaic devices, light-emitting diodes, antireflection coatings and biological devices. Moreover, a new phase-change material might be found to have the best germanium, antimony and tellurium (Ge-Sb-Te) alloy. The goal was to find the best contrast between the crystalline and amorphous states and they are used for electronic device memory either DRAM or Flash chips finally. For polymer solutions, many approaches and techniques have been used to determine the coexistence curve including the lower critical solution temperature (LCST) and the upper critical solution temperature (UCST). A modified centrifugal apparatus for measuring the coexistence curves of a polymer solution: polystyrene solution in methyl cyclohexane is reported for the first time in research laboratory. The polymer blend phase separation morphology is applied to the lithography patterning for the first time. And it is then invented as a patent and proposed for industrial application by the author of this book this year.