The interface formed between two immiscible electrolyte solutions (ITIES) constitutes a fantastic playground for the investigation of charge (under the form of either ion or electron) transfer processes. We have reviewed here the routes for the modification of such soft interfaces by an accurate electrochemical control. The three main strategies developed in the past four decades include (i) the electrochemically controlled assembly of molecules and nano-objects; (ii) the in situ electrogeneration of nanomaterials and (iii) the use of ex situ synthesized membranes. Applications of functionalized ITIES in the fields of redox catalysis and electroanalysis of modified soft interfaces are also discussed.