Growth is concentrated on either side of the heart tube, while deformation dominates the central region, stretching the middle of the heart tube along the head-to-tail axis. These coordinated movements cause the medial heart tube to bulge outward, while two ring-like regions on the sides remain relatively constrained, giving the developing heart tube the shape of a barrel. This model predicts movements of simulated cells within the dynamic heart tube model, closely matching measured trajectories from labeled cells in living embryos. Accordingly, the researchers followed several pseudo-cell clusters along the heart tube and observed cellular rearrangements that support their proposed barrel model of heart tube formation. Raiola et al.