For years, animals have been the main source for experimentation in the lab and while there has been some effort put towards creating new artificial techniques (which don't involve the potential suffering of a living creature), they are still the most common, and best, model available for testing the presentation and treatment of various diseases. Despite this, they come with huge problems - they're expensive, their use raises many ethical questions and they're often too different from us to be completely reliable. One attempt at creating an alternative is the creation of brain organoids: brains which have been grown from human stem cells, which could be tested alone or transplanted in to an animal for research. It could allow us to look at the human brain in ways we never thought possible.
However, the technique has caused some concerns within the scientific community as many worry that it is equivalent to human testing. “We’re already seeing activity in organoids that is reminiscent of biological activity in developing animals,” said Elan Ohayon, the director of the Green Neuroscience Laboratory in San Diego, “We don’t want people doing research where there is potential for something to suffer.”
Could an organoid be sentient? Are these brains waking up as alternative versions of ourselves, à la the "cookies" in the Black Mirror universe? Hank Greely, the director of the Center for Law and the Biosciences at Stanford University, doesn't think so - saying “I’m confident they don’t think we’ve reached a state, where a person wakes up and finds he is an organoid. I strongly doubt that anyone has reached that point or come close to it." However, he does raise concerns for the future and thinks debates on the topic are very important to ensure the correct ethical guidelines are in place.