New synthetic methods in polymer chemistry developed over the last twenty years and advances in materials characterization tools have enabled the creation of highly defined, discrete polymers. The advances in chemistry allow for the targeting of specific molar masses with low molar mass distributions, which in turn allows for more direct studies of structure-to-property relationships, including matching experimental results more closely with theory. Facile, one-pot synthesis of diblock copolymers to high monomer conversion, without the need to stop and purify after each addition, have enabled precise control over molar masses with high degrees of chain end fidelity and where each block has a discrete, known composition. When the blocks are chosen to be chemically incompatible e.g. immiscible, they can undergo interesting self-assembly behavior to form spherical, hexagonally packed, gyroid, and lamellar architectures, depending on the degree of polymerization, volume fractions of each block, and the repulsive interactions between the monomers. As each of the blocks can be precisely known down to each degree of polymerization, this enables the construction of accurate phase diagrams with high degrees of certainty for these materials. This helps develop a closer match between experimentalists and theorists looking to design new materials with never-before-seen phases and properties, ultimately advancing the applications of block copolymers in nanotechnology.