Microscopic silica bodies that form in living plants, providing a durable floral ecofact that allows identification of plant remains in archaeological deposits.

It is a fossilized part of a living plant that secreted opal silica bodies and it is found within the cells of certain plants; especially, grasses and cereals.

These silica bodies are often able to survive after the organism has decomposed or been burned. They are common in ash layers, pottery, and even on stone tools used to cut the stems of silica-rich plants (for example, cereals).

Different plants produce phytoliths with different characteristic shapes and sizes, although not all are unique to specific species. These can be detected by an electronic scanning microscope.