Particles nodes (NukeX only) deal with Nuke's built-in particle system, often used for creating effects like fog, smoke, rain, snow, and explosions.
NOTE: Loading example scripts only works if you launched the online help from Nuke and have set documentation source to local on the Control Panels tab of the Preferences.
Using particles to simulate fireworks
Using particles to simulate smoke
Using particles to simulate an electricity ball
Using particles to simulate a blue light trail
Using ScanlineRender and VectorBlur to add motion blur to particles
See also the particles tool sets available in Nuke's ToolSet menu.