Assemblies of molecular aggregates in the blebbing motion of an oil droplet on an aqueous solution containing surfactant

•The amoeboid dynamics of an oil droplet on an aqueous solution is investigated.•The surface tension change of the aqueous phase explains the droplet behavior.•Domains of branched assemblies of molecular aggregates form at the droplet bottom.•The heterogeneous adsorption of assemblies at the rim initiates the bleb growth.