How is a newborn star formed? For the answer to this question, we must look to the familiar physical concept of gravitational instability. It is a simple concept, long known to scientists, having been first recognized by Isaac Newton in the late 1600s. Let us envision a cloud of interstellar atoms and molecules, slightly admixed with dust. This cloud of interstellar gas is static and uniform. Suddenly, something occurs to disturb the gas, causing one small area within it to condense. As this small area increases in density, becoming slightly denser than the gas around it, its gravitational field likewise increases somewhat in strength. More matter now is attracted to the area, and its gravity becomes even stronger; as a result, it starts to contract, in process increasing in density even more. This in turn further increases its gravity, so that it accumulates still more matter and contracts further still. And so the process continues, until finally the small area of gas gives birth to a gravitationally bound object, a newborn star.