header Browsers that should work include the latest versions of Firefox, Google Chrome, Safari and Opera. Version 9.0 of Internet Explorer may also work. graphic Walk Directions walk-directions Sticky Directions sticky-directions Probability of Sticking 1.00 Particle Size 1.5 Maximum Particle Number 100000 sliders Random Walk Ballistic Walk radios Run Erase Defaults Capture controls content The bit-player banner illustrates a process called diffusion-limited aggregation. Particles drift freely through a two-dimensional space until they hit the bottom or touch another particle that is already in contact—directly or indirectly—with the substrate. When thousands of particles are deposited in this way, the result is a feathery or frondlike pattern, resembling a number of structures seen in nature. The colors ref...