In this talk I will describe a new method of measuring the physical conditions of the neutral ISM in high redshift galaxies by measuring the fine structure lines of carbon and silicon in Damped Lyman Alpha systems (DLAs). The method is able to measure the volume density and temperature of the gas simultaneously. The results from this study suggests that the physical conditions of neutral gas can vary significantly from one galaxy to another. I will compare these results with previous studies of DLAs and how these results fit in with the cold neutral medium/warm neutral medium paradigm of the high redshift universe. Furthermore, I will highlight how new observations using ALMA are able to further our understanding of the physical conditions of gas in high redshift galaxies.