To arrive at functional organic materials with optimal molecular organization, control over the aggregation process is a prerequisite. Often however, multiple pathways are involved that compete for the same molecular building block, a phenomenon known as pathway complexity. As a result, the material–made from small molecules or polymers–can get entrapped in a metastable pathway while a more stable, but slower formed morphology is aimed for. Vice versa, the equilibrium state can be obtained easily but another, less stable morphology is desired as it has more interesting properties. In both cases, the solution processing, starting from molecularly dissolved material, should be optimized to select the desired aggregation pathway. This perspective aims to outline the importance of mechanistic insights derived from self-assembly of 1D fibers in diluted solutions to unravel and control aggregation pathways involved in the processing of p-conjugated materials.