For thirteen billion years, light battled through cosmic emptiness. It bent around massive galaxy clusters that, as Einstein predicted, acted as giant lenses — amplifying and distorting the distant glow. In 2023, the NIRSpec instrument on the James Webb Space Telescope captured this light and spread it into spectra. An unexpected picture emerged: tiny galaxies, born just half a billion years after the Big Bang, contained surprisingly large amounts of nitrogen. Thus began an investigation linking the chemistry of the ancient cosmos to the mysteries of modern globular clusters.

Astronomers collected 405 such distant spectra and applied stacking techniques. They divided them into groups by stellar mass, from millions to billions of Suns, and took the median. The faint whisper of individual objects merged into a clear chorus. Emission lines of oxygen, carbon, and nitrogen appeared. Special attention was drawn to the ultraviolet nitrogen line Niv] 1483,1486. It showed 25 times more nitrogen than optical estimates. Hot, highly ionized gas regions were saturated with it. It seems special star chefs were at work there. The lowest-mass stack, about 4 million Suns, had a metallicity (fraction of elements heavier than helium) of only 2% solar. Apparently, early supernovae were actively blowing out gas, preventing heavy elements from accumulating.

The prime suspects are Wolf–Rayet stars. This is a brief final stage in the life of very massive stars. Back in the mid-20th century, Margaret Burbidge, Fred Hoyle, and Hans Bethe described how nuclear reactions forge carbon and oxygen in stellar interiors. But in giants at the Wolf–Rayet stage, the CNO cycle proceeds further, converting these elements into nitrogen. Monstrous stellar winds blow it into space. Estimates show that to explain the observed helium emission, a typical dwarf galaxy must host about 1650 such 'chefs.' Their combined winds can enrich an entire globular cluster with a mass of 200 thousand Suns with nitrogen. The chemical pattern (low carbon, high nitrogen, and neon like the Sun) exactly matches what is seen in stars of modern globular clusters. Dwarf galaxies in the early universe were likely the kitchens where ingredients for future generations were prepared.

Spectroscopy and redshift (the Doppler effect for the expanding universe) allowed us to peek into an era when the mass–metallicity relation was just forming. New surveys, such as VENUS, will increase the sample of lensed objects tenfold. The Extremely Large Telescope (ELT) will be able to resolve individual star formation regions in these distant systems, and then we will see where exactly star chefs are working right now. After 13 billion years, the light still carries their recipes, and teaches us to read the cosmic cookbook.