It’s a remarkable first for the scientific community: astronomers in Europe have witnessed star-forming gas clouds in the early universe, which represent the building blocks of the very first galaxies.

The European Southern Observatory’s ALMA telescope in Chile was used to make the discovery, as scientists looked deep into space and past the galaxies in the foreground to spot the faint glow of ionized carbon, according to a UPI report.

Astronomers were trying to glimpse some of the oldest known galaxies in the universe, dating back to just 800 million years after the Big Bang, when they spotted a signal of glowing carbon on the side of galaxy BDF 3299.

Andrea Ferrara, an astronomer from Italy’s Scuola Normale Superiore and a co-author study, said that this is the most distant detection ever of such an emission, according to the report. This allows scientists to watch galaxies in the early stages of their development.

Scientists believe that at the beginning of time, space was filled with gas clouds, and as stars began to form, the dust began to clear in a process that is called reionization.

Researchers believe they have spotted this dust before it collapsed into stars via ALMA, and it was spotted near BDF 3299 because newly formed stars had cleared the dust out of the center of the galaxy.

This is a big deal to scientists because they’ve been trying to understand the “interstellar medium” and the formation of stars and galaxies, Ferrara said according to the report.

Reionization is a term used in Big Bang cosmology to describe the process of reionizing matter in the universe, the second of two ajor phase transitions of gas. The first phase is the change of hydrogen in the universe, a process called recombination.