a, Schematics showing the workflow for NANP production. b,c, Two main design strategies: the first relies on intramolecular bonds within each monomer that promote the formation of magnesium-dependent interacting motifs required for intermolecular interactions (b), and the second is based on assembly of NANPs and individual monomers designed to form intermolecular bonds only with their cognate partner strands (c). Scale bars, 500 nm (main); 100 nm (insets). 3WJ, three-way junction; PK, pseudoknot; SELEX, systematic evolution of ligands by exponential enrichment; Us, uracils.