The Download: Mice with Part-Human Brains and Climate Tech Innovators
Plus: US and Chinese experts have proposed nuclear-style AI safeguards.
By Thomas Macaulay | September 17, 2026
This is today's edition of The Download, our weekday newsletter that provides a daily dose of what's going on in the world of technology.
Meet a Mouse Whose Brain Cortex Is Made Up of Human Cells
Multiple cameras tracked a mouse as it wandered around a small arena. A computer charted its position and speed, leaving Pong-like traces on a monitor. The reason to watch this rodent so carefully? Nearly half its brain volume had been replaced with human cells.
A team at Stanford revealed this week that it had undertaken the effort to mix brain tissues from distant species. The researchers had previously shown that human brain organoids could survive, and even function, after being injected into the heads of baby rodents. Now, they've taken things a step further by genetically modifying mice so their brains don't fully develop in the first place.
The work could help scientists study brain injuries, but it also raises questions about how far these experiments should go.
Here's what the researchers discovered—and where they draw the line.
—Antonio Regalado
These Innovators Under 35 Are Shaping the Future of Climate Tech
(Content continues below—full article available via MIT Technology Review.)
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