In constructing fully functional whole skin grafts with complete functionality using 3D bioprinting, how to precisely regulate the composition of the bioink, the cell distribution and the printed structure so as to not only achieve traumatic coverage in the short term, but also maintain the elasticity of the skin, the barrier function, and the regeneration of the appendages (e.g., sweat glands and sebaceous glands) over time in order to achieve a high degree of resemblance to the natural skin? What are the key challenges that need to be solved in each step of the process, from cell sourcing, growth factor piggybacking to post-construction vascularization strategies?