Here's a simplified explanation of the process:

1. Rapid Burial: An organism dies and is quickly buried under sediment (like sand, mud, or volcanic ash). This prevents decomposition and decay.

2. Permineralization: Minerals dissolved in groundwater seep into the buried organism's pores and spaces. These minerals crystallize, replacing the original organic matter with rock.

3. Replacement: Over time, the original material is entirely replaced by minerals, leaving behind a hardened, stone-like replica of the organism.

There are different types of fossilization, but permineralization and replacement are the most common.