Henry Molaison, also called H.M., was a very important person in the history of brain studies. He had a problem with his brain that made it hard for him to remember things - something we all do every day!
Scientists studied H.M. for many years to learn more about how our brains work. They found that he had a part of his brain removed called the hippocampus, which is important for making new memories.
Without his hippocampus, H.M. couldn't remember things that happened after his surgery. But he could remember things from a long time ago, like childhood memories.
Scientists learned a lot from H.M. They found out more about how our brains make memories and how different parts of our brains work together. H.M. helped us understand more about how our brains work, and we're still learning from his case today!