Grown from human stem cells, organoids are clusters of living cells that resemble parts of the human body. From intestines to kidneys, livers to brains, these biological structures mimic how organs develop in the womb, and represent a major step forward in medical research. ... What are some of the scientific and clinical frontiers that organoids are allowing us to probe? Where do they sit on the spectrum between ‘persons’ and ‘things’, and what ethical challenges do they present? Is there a possibility that brain organoids could display signs of consciousness – and if so, how would we know?