- Polydiacetylenes (PDAs) constitute a family of conjugated amphiphilic polymers that display unique color and fluorescence properties. Described is the hierarchical assembly of micrometer-sized tubes that comprise a melamine-substituted PDA derivative. The nano- to microscale transformations of the amphiphilic building blocks were induced by addition of divalent metal ions. The PDA microtubes facilitated the high-sensitivity fluorescence detection of bacteria. Totally tubular: A hierarchical assembly of microscale tubes that comprise a melamine-substituted polydiacetylene (PDA) derivative was achieved by the addition of Zn2+ ions (see figure). This study demonstrates nano- to microscale hierarchical transformations of amphiphilic building blocks.