Biomembranes form the outer boundary of cells and define distinct internal compartments. Curvature energies of Canham-Helfrich type play a central role in understanding membrane mechanics and present intriguing challenges for mathematical analysis. In this talk we present joint work with Fabian Rupp (Vienna) on the minimization of a reduced Canham-Helfrich energy among closed surfaces confined within a prescribed container. We establish an existence result in a class of immersed bubble trees, derive the corresponding Euler–Lagrange equation, and investigate regularity properties of minimizers.