Method for producing core-shell microcapsules comprising a core containing at least one active ingredient, said core being surrounded by a polymer shell formed of 50 to 100 % by weight of a silsesquioxane compound relative to the total weight of said shell, said method comprising the steps of: i) dispersing at least one lipophilic or hydrophilic active ingredient in a continuous aqueous or organic phase respectively, to form an oil-in-water or water-in-oil emulsion or dispersion respectively; ii) hydrolysing a precursor of the polymer compound of silsesquioxane type of formula R-SiO 3/2 where R is: - an alkyl radical having 1 to 20 carbon atoms, substituted or unsubstituted such as methyl, ethyl, n-propyl, isopropyl, 1-n-butyl, 2-n-butyl, isobutyl, tert-butyl, n-pentyl, isopentyl, neopentyl, tert-pentyl, hexyl, heptyl, octyl, 2,2,4-trimethylpentyl, nonyl, decyl, dodecyl, octadecyl, cycloalkyl, aryl, alkaryl and aralkyl radicals; - an oxygenated alkyl radical such as methoxyethyl and ethoxyethyl, - a halogenated radical such as chloropropyl, 3,3,3-trifluoro-n-propyl, 2,2,2,2',2',2'-hexafluoroisopropyl, heptafluoroisopropyl, o-, m- and p-chlorophenyl; - or an unsaturated radical such as vinyl, 5-hexenyl, 2,4-divinylcyclohexylethyl, 2-propenyl, allyl, 3-butenyl, 4-pentenyl, ethynyl, propargyl and 2-propynyl, and in situ polymerisation thereof in or in contact with the aqueous phase of the oil-in-water or water-in-oil dispersion or emulsion, to form a silsesquioxane homopolymer or copolymer; characterized in that (iii) adding to the organic phase of the microcapsules, at the start of the hydrolysis and/or polymerisation reaction, of a compound selected from among: - a silicate, preferably water-insoluble in the hydrolysed state, such as ethyl polysilicate, - a precursor of the polymer compound of silsesquioxane type, - or mixtures thereof and in that the polymerisation step is conducted in an acid medium, so as to impart an interfacial nature to polymerisation or encapsulation, to promote imperviousness of the microcapsules. i) dispersing at least one lipophilic or hydrophilic active ingredient in a continuous aqueous or organic phase respectively, to form an oil-in-water or water-in-oil emulsion or dispersion respectively; ii) hydrolysing a precursor of the polymer compound of silsesquioxane type of formula R-SiO 3/2 where R is: - an alkyl radical having 1 to 20 carbon atoms, substituted or unsubstituted such as methyl, ethyl, n-propyl, isopropyl, 1-n-butyl, 2-n-butyl, isobutyl, tert-butyl, n-pentyl, isopentyl, neopentyl, tert-pentyl, hexyl, heptyl, octyl, 2,2,4-trimethylpentyl, nonyl, decyl, dodecyl, octadecyl, cycloalkyl, aryl, alkaryl and aralkyl radicals; - an oxygenated alkyl radical such as methoxyethyl and ethoxyethyl, - a halogenated radical such as chloropropyl, 3,3,3-trifluoro-n-propyl, 2,2,2,2',2',2'-hexafluoroisopropyl, heptafluoroisopropyl, o-, m- and p-chlorophenyl; - or an unsaturated radical such as vinyl, 5-hexenyl, 2,4-divinylcyclohexylethyl, 2-propenyl, allyl, 3-butenyl, 4-pentenyl, ethynyl, propargyl and 2-propynyl, and in situ polymerisation thereof in or in contact with the aqueous phase of the oil-in-water or water-in-oil dispersion or emulsion, to form a silsesquioxane homopolymer or copolymer; - an alkyl radical having 1 to 20 carbon atoms, substituted or unsubstituted such as methyl, ethyl, n-propyl, isopropyl, 1-n-butyl, 2-n-butyl, isobutyl, tert-butyl, n-pentyl, isopentyl, neopentyl, tert-pentyl, hexyl, heptyl, octyl, 2,2,4-trimethylpentyl, nonyl, decyl, dodecyl, octadecyl, cycloalkyl, aryl, alkaryl and aralkyl radicals; - an oxygenated alkyl radical such as methoxyethyl and ethoxyethyl, - a halogenated radical such as chloropropyl, 3,3,3-trifluoro-n-propyl, 2,2,2,2',2',2'-hexafluoroisopropyl, heptafluoroisopropyl, o-, m- and p-chlorophenyl; - or an unsaturated radical such as vinyl, 5-hexenyl, 2,4-divinylcyclohexylethyl, 2-propenyl, allyl, 3-butenyl, 4-pentenyl, ethynyl, propargyl and 2-propynyl, - a silicate, preferably water-insoluble in the hydrolysed state, such as ethyl polysilicate, - a precursor of the polymer compound of silsesquioxane type, - or mixtures thereof