(A) Fluorescence image of neonatal rat cardiomyocytes in static conditions and after 24 h of cyclic stretch (1 Hz). Stained for Cx43 (green) and N-Cadherin (red) and counterstained with DAPI (blue). Junction proteins display an unorganized distribution in static conditions compared to localized distribution after cyclic stretch 94. (B) Average contraction stress in mN/mm2 of hESC-CM, hiPSC-CM, and human fetal cardiomyocytes at 14 weeks, 17 weeks, and 19 weeks. ns = non-significant; *P < 0.05; **P < 0.01; ***P < 0.001 47. Reproduced with permission from Elsevier. (C) Contraction stress map for a contracting day 30 hPSC-CM showing the range and localizations of contraction stresses 77. This is an open access article distributed under the Creative Commons Attribution License. (D) Volume percentages occupied by the nucleus, sarcomere, and mitochondria in non-stimulated and stimulated neonatal rat ventricles, and native heart. (E) Frequency of intercalated discs (IC) and gap junctions in non-stimulated and stimulated neonatal rat ventricles and native heart. * denotes statistically significant differences between the groups (P <0.05; Tukey's post hoc test with one-way ANOVA) 139. Copyright 2004 National Academy of Sciences.