Star clusters form in dense, hierarchically collapsing gas clouds. Bulk kinetic energy is transformed to turbulence with stars forming from cores fed by filaments. In the most compact regions, stellar feedback is least effective in removing the gas and stars may form very efficiently. Knowing the age of CSCs, and then red shifting them to form a specific cosmic science, is a key parameter for understanding their relationship to galaxy formation and for testing model predictions. Knowing the lifespan of GCs provides a strict limitation to GC formation models. The formation of globular clusters is still remains poorly understood
