Axolotls are salamanders that reach sexual maturity while still in their larval form, keeping their feathery external gills and remaining fully aquatic throughout life. Named from the Nahuatl word for water monster, they once thrived in Mexico's highland lakes around Mexico City. Today, fewer than 1,000 wild axolotls remain, driven nearly extinct by invasive fish and habitat destruction. Yet they've found unexpected fame in laboratories and aquariums, valued for their remarkable ability to regenerate lost limbs, gills, and even parts of their brains and eyes.