Here for simplicity, we considered two types of deformations: (i) In long timescale, the surface area A was assumed to be conserved, while the volume V was allowed to change to keep a ixed osmotic pressure p. (ii) In short timescale, the volume V was assumed to be conserved, while the surface area A was allowed to change to keep a ixed membrane tension σ. Our calculation results showed that the stable shapes under the two conditions are similar, therefore, we presented the results for type (i) deformation in the main text, while leaving the results for type (ii) deformation in the Supplementary Information (Figs. ).