Molecular-thermodynamic models are applied to network-forming systems of three types: (1) wormlike micelles of ionic surfactant, (2) water + oil + surfactant mixtures, and (3) mixtures of reversibly associating chainlike molecules. For ionic surfactants, we illustrate the stabilization mechanism for the bilayer perforation that has a toroidal rim and describe the sequence of shape transitions induced by adding salt, including formation of bicontinuous structures and branched versus nonbranched wormlike micelles. For both ionic and nonionic surfactants, we show the zones of stable perforated bilayers and stable branched structures in an extended state diagram of a microemulsion derived from the Helfrich-Safran curvature expansion. For mixtures of reversibly associating sticky chains, our molecular dynamic (MD) simulations demonstrate crowding: an enhancement of association caused by the presence of chains that carry nonsticky monomers. An easy-to-use mean-field correction to the apparent association constant gives a good prediction of this effect. For an equilibrium physical gel formed by sticky chains, our MD data show large presence of cyclic structures.