Overall, the bulk GelMA-CBP hydrogels showed compatibility with 3T3 fibroblasts, which presented high viability over time. Next, mesh-like constructs were fabricated through extrusion 3D bioprinting at 37 ºC and crosslinking using 405 nm light from 5%GelMA-0.5%CBP-0.5%LAP bioinks with cells incorporated at two densities: 0.5 x 10 6 and 5 x 10 6 cells/mL (Figure ). All the bioprinted constructs showed cell viability within the hydrogels > 90% over the 14 days of culture (Figure ). Cell morphology within the hydrogels depended on the cell density used in the bioink (Figure ). The lower density (0.5 x 10 6 cells/mL) resulted in cells with rounded morphology, while the higher density (5 x 10 6 cells/mL) led to fibroblasts that changed over time from a rounded to an elongated morphology. This finding highlights the key role that bulk cell density plays in the cellular morphology within 3D microenvironments. These findings are consistent with previous reports, where low cell densities have been shown to negatively impact the elongation of fibroblasts bioprinted within GelMA-based bioinks. Although the fibroblasts showed an elongated morphology that more closely resembled that observed for cells on 2D surfaces, cellcell interactions were limited, suggesting hindrance due to a small pore size within the bulk hydrogel. It is worth noting that a different morphology progression was observed between the bioprinted and those in the cast pucks when the same bioink composition and cell density were used. We attribute the differences in cell morphology outcome to the size of the bioprinted constructs, where the width of the meshes are in the sub-millimeter range, while the bulk puck hydrogels are millimeter in diameter and thickness. These differences could impact the transport of nutrients within the 3D microenvironments as well as change the proximity of the cells to an external "surface" that could lead to elongation of cells. This is supported by literature reports that show that 3T3 fibroblasts display more elongated morphologies within micropatterned GelMA constructs than within a bulk hydrogel. These results reveal a clear advantage of using thin 3D bioprinted scaffolds with sub-millimetre features over mold cast materials for 3D cell culture experiments and biomimetic models. CBP surfaces was expected given the presence of RGD motifs in GelMA. To quantitatively evaluate the different morphologies within and on top of the GelMA-CBP materials, we measured the cell area over time (Figure ). In agreement with our qualitative observations, when cells were bioprinted at a density of 0.5 x 10 6 cells/mL, they remained rounded without significant changes in the area. Conversely, when the cell density was increased to 5 x 10 6 cells/mL, we observed a statistically larger area. This trend was more marked at days 7 and 14, in agreement with our qualitative observation of fibroblast elongation at higher cell density in the bioink.