A formulation in nanoemulsion form comprising a continuous aqueous phase and a least one dispersed phase, and comprising: - at least 5 mole % of amphiphilic lipid; - 15 to 70 mole % of at least one cationic surfactant comprising: - at least one lipophilic group selected from among: - an R or R-(C=O)- group, where R is a linear hydrocarbon chain having 11 to 23 carbon atoms, - an ester or amide of fatty acids having 12 to 24 carbon atoms and phosphatidylethanolamine, and - a poly(propylene oxide), and - at least one hydrophilic group comprising at least one cationic group selected from among: - a linear or branched alkyl group having 1 to 12 carbon atoms and interrupted and/or substituted by at least one cationic group; and - a hydrophilic polymeric group comprising at least one cationic group; and - 10 % to 55 mole % of a co-surfactant comprising at least one poly(ethylene oxide) chain comprising at least 25 ethylene oxide units; - a solubilising lipid, - optionally a helper lipid, - optionally an oil, - optionally an imaging agent, and - optionally a lipophilic therapeutic agent, wherein the mole percentages of amphiphilic lipid, cationic surfactant and co-surfactant are relative to the whole (amphiphilic lipid / cationic surfactant / co-surfactant / optional helper lipid), and wherein the mole proportion of the whole (solubilising lipid / optional oil / optional imaging agent / optional lipophilic therapeutic agent) relative to the dispersed phase is 10 to 80 %. - at least 5 mole % of amphiphilic lipid; - 15 to 70 mole % of at least one cationic surfactant comprising: - at least one lipophilic group selected from among: - an R or R-(C=O)- group, where R is a linear hydrocarbon chain having 11 to 23 carbon atoms, - an ester or amide of fatty acids having 12 to 24 carbon atoms and phosphatidylethanolamine, and - a poly(propylene oxide), and - at least one hydrophilic group comprising at least one cationic group selected from among: - a linear or branched alkyl group having 1 to 12 carbon atoms and interrupted and/or substituted by at least one cationic group; and - a hydrophilic polymeric group comprising at least one cationic group; and - at least one lipophilic group selected from among: - an R or R-(C=O)- group, where R is a linear hydrocarbon chain having 11 to 23 carbon atoms, - an ester or amide of fatty acids having 12 to 24 carbon atoms and phosphatidylethanolamine, and - a poly(propylene oxide), and - an R or R-(C=O)- group, where R is a linear hydrocarbon chain having 11 to 23 carbon atoms, - an ester or amide of fatty acids having 12 to 24 carbon atoms and phosphatidylethanolamine, and - a poly(propylene oxide), and - at least one hydrophilic group comprising at least one cationic group selected from among: - a linear or branched alkyl group having 1 to 12 carbon atoms and interrupted and/or substituted by at least one cationic group; and - a hydrophilic polymeric group comprising at least one cationic group; and - a linear or branched alkyl group having 1 to 12 carbon atoms and interrupted and/or substituted by at least one cationic group; and - a hydrophilic polymeric group comprising at least one cationic group; and - 10 % to 55 mole % of a co-surfactant comprising at least one poly(ethylene oxide) chain comprising at least 25 ethylene oxide units; - a solubilising lipid, - optionally a helper lipid, - optionally an oil, - optionally an imaging agent, and - optionally a lipophilic therapeutic agent,