This project aims to make pioneering measurements of hidden gas in our Milky Way Galaxy. The dynamic transformation of diffuse gas to dense clouds and then to stars is a crucial component of how galaxies function. Recent work implies vast reservoirs of undetected gas that is intermediate between the diffuse and dense phases - a vital missing link connecting diffuse gas to star-forming clouds. This project aims to uncover that hidden gas, using state-of-the-art radio spectral line observations and innovative theoretical models to understand its role as an intermediary on the road to star formation. These high-impact results would challenge our understanding of how galaxies form and evolve from the early universe to the present day.