Molecular clouds are regions within interstellar space where molecular hydrogen and other small molecules such as carbon monoxide and ammonia are abundant. These clouds are cold and dense, with temperatures ranging from 10 to 30 Kelvin and densities of up to 10^4 molecules per cubic centimeter. Molecular clouds are the birthplaces of stars, with the gravitational collapse of a cloud leading to the formation of new stars and planetary systems. These clouds are often observed using radio telescopes and infrared telescopes, as the cold temperatures make them difficult to detect in visible light. Studying molecular clouds is essential for understanding the processes of star formation and the evolution of galaxies.