ECFC vascular network growth and complexity in HA hydrogels (day 3). (A) Left panel: Growth of comprehensive vascular networks are demonstrated using LM images at low magnification. Right panel: (i and ii) are high magnifications of white boxes (arrows indicate branched and elongated vascular networks). Scale bars are 100 μm. (B) Confocal analysis of vacuole vital stain FM 4-64 (cyan; nuclei in blue) demonstrating large lumen within the networks, and (C) demonstrated using orthogonal view (indicated by arrowhead). Scale bars are 50 μm. (D) TEM high-resolution images show cross-sections of matured vascular tube networks with enlarged lumens. Scale bars are 20 μm.