Even after 20 million years of evolutionary separation, two tiny worm species show astonishingly similar patterns in how they turn genes on and off. Scientists mapped every cell s activity during development and found that genes essential to basic functions like muscles and digestion remained largely unchanged. Meanwhile, genes linked to sensing the environment or brain-like functions showed more variation. This high-resolution comparison of every cell between species may help unlock mysteries of how life evolves and adapts without always changing how it looks.