An advanced human heart organoid system can be used to model embryonic heart development under pregestational diabetes-like conditions, researchers report. The organoids recapitulate hallmarks of pregestational diabetes-induced congenital heart disease found in mice and humans. The findings also showed that endoplasmic reticulum (ER) stress and lipid imbalance are critical factors contributing to these disorders, which could be ameliorated with exposure to omega-3s.