Time machine: detailed near-infrared images of galaxies that existed when the universe was only 900 million years old. The images were taken by the JWST as part of a study of reionization in the early universe. Courtesy: NASA, ESA, CSA
What about it?
Reionization is the process by which neutral hydrogen atoms are ionized, making the universe transparent to light at wavelengths that would have been absorbed by the atoms.