Ultra-small liposomes (<50 nm) are ideal for tissue penetration yet inherently unstable due to extreme membrane curvature. Here, we discover that triterpenoids—plant-derived amphiphilic molecules—resolve this paradox by functioning as dual-action membrane modulators. These compounds impose positive spontaneous curvature to drive nanoscale budding into ultra-small (≈20 nm) lipid nanocages, while establishing a hydrogen-bond network that reinforces bilayer cohesion. The resulting ultra-small (≈20 nm) nanocages are structurally robust and withstand thermal, chemical, and mechanical challenges far beyond conventional liposomes. When applied to human skin model, these nanocages distribute across epidermal and dermal layers and deliver hydrophobic cargo 7.8-fold more effectively than conventional liposomes. This work opens new avenues for developing robust nanocarriers in pharmaceuticals and cosmetics, eliminating the classical size-stability trade-off.