Cell shapes in the atrium are represented by scaled ellipsoids for the same heart at 36 hpf (a), 44 hpf (b), and 52 hpf (c). Ventricular cells are shown with reduced opacity. (d, e, f) The same cells as in (a, b, c) with additional color code indicating cell size. Smaller cells are shown in blue, larger cells in red, highlighting the increase in cell size, in particular along the larger curvature of the atrium. Changes in cell size shown as 2D projections for 36 (g), 44 (h), and 52 hpf (i). The color code indicates normalized cell size as in (d, e, f). Isosize lines shown in black (ΔA = 0.1).