The fibroblasts inside the constructs displayed a rounded morphology even after 14 days. It is known that cells display a different morphology when grown as monolayers on 2D substrates than in 3D environments, even when cultured on top of a 3D material. When fibroblasts are seeded onto a 2D surface, they tend to spread and elongate, while in a 3D environment this does not necessarily occur. The porosity of the material seems to play a key role in the cell's morphology, with larger pore sizes required to yield elongated fibroblasts. In addition, when cells are encapsulated in bulk hydrogels, lack of pore interconnectivity and small pore size can limit cell elongation and migration, which we postulate is the main reason for the 3T3 fibroblasts remaining in a rounded morphology within our bulk material. It was also observed that the pucks contracted over time, with ca. 25% and 10% contraction for the 1% and 5% GelMA bioinks, respectively (Figure ). There were no significant differences in contraction between the pucks with and without cells, indicating that this behaviour is intrinsic to the materials and not due to remodelling or stress being exerted by the cells. We speculate that this phenomenon is related to the interaction of the CBP, which is rich in carboxylate groups, with ions in the cell culture media.