Correction to: Nature Biomedical Engineering https://doi.org/10.1038/s41551-018-0271-5, published online 23 July 2018.

The commercially available human cardiac-muscle cells that we used in the study reported in this Article were ‘Cor.4U pluripotent-stem-cell-derived cardiomyocytes’, obtained from Axiogenesis (now NCardia). However, Ncardia has informed all customers that these cells show the DNA fingerprint of a specific embryonic stem-cell line, which suggests that these cardiomyocytes were differentiated from human embryonic stem cells rather than derived from cells reprogrammed into induced pluripotent stem cells. The findings reported in the Article remain valid in the context of demonstrating the feasibility of generating tissue-engineered heart chambers using human stem-cell-derived cardiomyocytes or primary rat cardiomyocytes. The work remains applicable to drug discovery, disease modelling and regenerative medicine, but care must be taken when extending the results reported in the Article to patient-specific applications. We also note that the Supplementary Information of the Article includes data using cardiomyocytes derived from human induced pluripotent stem cells obtained from the Personal Genome Project PGP1 cell line.