Porous organic polymers represent a rare class of materials that combine high internal surface area with broad-spectrum chemical stability. These features make them attractive for applications where surface-guest interactions and durability dictate performance, including corrosive gas storage, water purification, energy storage, and catalysis. In many cases, performance can be improved by fine-tuning bulk microporosity, yet factors affecting this key property remain poorly understood. This seminar describes efforts to identify how synthetic pathways shape microporosity in amorphous porous networks. Using a network disassembly approach, we show that pathway-dependent porosity is largely driven by defects arising from incomplete cross-linking. Implications for synthetic design and selected biomedical applications of highly microporous organic polymers will also be discussed.