What term describes the process that made the universe transparent, allowing light to travel freely for the first time?

Answer

Recombination

Recombination occurred when the universe cooled enough (around 380,000 years old) for protons and electrons to combine into neutral hydrogen atoms, ending the opaque state.

What term describes the process that made the universe transparent, allowing light to travel freely for the first time?
Originsciencetheoryuniversecosmology