In October 2023, an international group of scientists released an impressively detailed cell atlas of the human brain, published in 21 papers in the journals Science, Science Advances and Science Translational Medicine.The human brain has roughly 171 billion cells, which makes it a herculean task to categorize them all. Scientists collected samples from different parts of the brain and have identified 3,000 different types of cells. Each cell contains thousands of genes and each cell type only expresses a small fraction of those. Cataloging cells by their gene expressions, paves the way for scientists to tailor disease treatments to target only the affected cells. This human brain cell atlas is only the first draft, but it could signal a paradigm shift in how we understand and treat neurological diseases.Ira talks with one of the researchers who helped put together the cell atlas, Dr. Ed Lein, senior investigator at the Allen Institute for Brain Science, and takes listener calls.Transcripts for each segment will be available the week after the show airs on sciencefriday.com. Subscribe to this podcast. Plus, to stay updated on all things science, sign up for Science Friday's newsletters.