This atlas contains more than 500 microscopy pictures resulting from the observation of multiphase polymer-based materials. These illustrations include micro and nanopolymer blends, micro and nanocomposites, micro and nano phases in copolymers, thermoplastic vulcanizates (TPVs), and thermosets and thermoplastic blends that were intensively developed during the past decade. Each picture includes a detailed explanation of how to attain these materials, how the samples were prepared, and how the observations were conducted. An introductory section evaluates the advantages and disadvantages of the various microscopic tools employed for investigating the phase morphology.