What causes particles to clump together in nebula?

Particles in a nebula clump together primarily due to gravitational attraction and collisions. As gas and dust particles collide, they lose energy, allowing them to stick together through processes like van der Waals forces or electrostatic attraction. Over time, these small aggregates grow larger, forming denser regions that can further attract surrounding material, leading to the formation of stars and planets. Additionally, pressure changes and turbulence within the nebula can enhance clumping by creating localized areas of higher density.