Molecular clouds are large, dense regions of gas and dust in interstellar space where new stars are born. These clouds are primarily composed of molecular hydrogen (H2) and can also contain other molecules such as carbon monoxide (CO), water (H2O), ammonia (NH3), and methanol (CH3OH). Molecular clouds are typically cold and have temperatures ranging from 10-20 Kelvin, allowing for the formation of complex molecules and dust grains. These clouds are important in the process of star formation, as gravity compresses the gas and dust within them, eventually leading to the collapse and ignition of a new star. Molecular clouds are studied using a variety of techniques, including radio and infrared observations, to understand the physical and chemical processes occurring within them.