Composite alginate hydrogels, a) Time sequential phase contrast micrographs shows HeLa and murine sarcoma SI80 spheroids encapsulated in media-core and alginate shell structure.203 Reproduced with permission from ref 203. Copyright 2013 National Academy of Sciences, b) Spatial assembly of core-shell structure. HepG2 cells confined in the media core and NIH/3T3 fibroblasts immobilized by the alginate shell forming an artificial liver in a drop.204 Reproduced with permission from ref 204. Copyright 2016 The Royal Society, c) Schematic illustration and micrographs of mouse ovary that consists of two mechanically distinct tissue layers consisting of a rigid cortex and a softer medulla.205 Reproduced with permission from ref 205. Copyright 2014 Elsevier, d) Alginate capsules with a Matrigel inner lining for human neural stem cells (hNSC) differentiation. Inset shows confocal image of the Matrigel forming a basement membrane-mimetic lining (red) on the inner surface of an alginate shell (green) microcapsule.209 Reproduced with permission from ref 209. Copyright 2016 The Royal Society. Scale bar: a, 100 μm; c, 100 μm; d, 10 μm.