Galaxy formation and evolution in the high redshift universe (z>1) are ever more getting attention and becoming more tangible in recent years thanks to various, unparalleled surveys at different wavelengths. Among many different approaches, probing the cold gas content and gas properties of galaxies is fundamental in the understanding of how star formation activities occur in the early universe. In this talk, I will present a brief review of observational studies in high redshift star-forming galaxies, largely focussing on the cold gas that was uncovered by the submm/mm-to-radio interferometry facilities including ALMA, NOEMA, and JVLA. The talk will consist of two main topics. The first half of the talk will cover cold gas content mostly from CO and dust observations, and the second half the interstellar medium properties probed by [CII] and other fine-structure lines at z>1. I will then wrap up the talk by introducing the current ongoing efforts and future prospects to overcome a few of the current challenges.