Printability of GelMA-CBP inks. The effect of GelMA and CBP concentrations on ink printability was assessed at 37 ºC by printing cylinder and mesh constructs (Figure ). The cylinders were used to qualitatively evaluate the ability of the inks to produce structurally robust constructs, while the meshes were used to quantitatively assess the printability figure of merit for each ink (Figure ). In general, all inks printed with high shape fidelity, structural stability, and printability at physiological temperature. Figure shows that, at a fixed 0.25% CBP, cylinder-like constructs with 1 cm height were successfully printed at all the concentrations of GelMA tested. The cylinders were able to support their weight and did not collapse, indicating that the mechanical properties were sufficient to maintain structural stability. Furthermore, the 3D printed constructs showed the ability to be stretched and return to original dimensions (Supplementary Information, Figure ), which indicates that these materials are suitable for dynamic tissue biomimetic constructs, e.g., for lung and muscle studies, where the stretching of the cell-laden structure is desired. In addition, the thickness of the cylinders decreased with increasing GelMA concentrations, which implies that at lower concentrations of the crosslinkable polymer the filaments can deform, resulting in broader structures that deviated from the designed shape; thinner, better-defined, and more accurate constructs were obtained from the inks with 7%