Crystallization-driven self-assembly of diblock copolymers into cylindrical micelles of controlled length has emerged as a promising approach to the fabrication of functional nanoscale objects with high shape anisotropy. Here we show the preparation of a series of crystallizable diblock copolymers with appropriate wettability and chemical reactivity, and demonstrate their self-assembly into size-specific cylindrical micelle building blocks for the hierarchical construction of mechanically robust colloidosomes with a range of membrane textures, surface chemistries and optical properties. The colloidosomes can be structurally elaborated post assembly by in situ epitaxial elongation of the membrane building blocks to produce microcapsules covered in a chemically distinct, dense network of hair-like outgrowths. Our approach provides a route to hierarchically ordered colloidosomes that retain the intrinsic growth activity of their constituent building blocks to permit biofunctionalization, and have potential applications in areas such as biomimetic encapsulation, drug delivery, catalysis and biosensing.Functional nanoscale objects can be prepared via crystallization-driven self-assembly of diblock copolymers. Here the authors show the self-assembly of crystalline block copolymers into size-specific cylindrical micelles for the hierarchical construction of mechanically robust colloidosomes with a range of membrane textures.