(A) Three-channel coaxial nozzles constructing tubular structure with switchable single/double layers (reproduced with permission from [69], Copyright 2018 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim); (B) Mice experiment of bioprinted vascular structures using Pluronic as sacrificial material (reproduced with permission from [25], Copyright 2017 Gao et al.); (C) Coaxial printing of double-layered, multi-layered, helical GelMA microfibers (reproduced with permission from [23], Copyright 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim); (D) Coaxial printing to build microfluidic bioreactor (reproduced with permission from [68], Copyright 2016 Elsevier).