How does pressure build up in a nebula?

Pressure in a nebula builds up primarily due to the gravitational attraction of gas and dust particles, which leads to an increase in density. As these particles clump together, their gravitational pull causes them to collapse inward, raising the temperature and pressure in the core of the forming structure. Additionally, processes like shock waves from nearby supernovae can compress the gas, further contributing to the buildup of pressure within the nebula. This increasing pressure is crucial for triggering nuclear fusion in stars as they form from the collapsing material.