1. Bacteria: These microscopic organisms are the primary decomposers. They break down organic matter, such as dead plants and animals, into simpler substances. This process is called decomposition.

2. Fungi: These organisms, like mushrooms and molds, also play a vital role in decomposition. They break down complex organic molecules, releasing nutrients back into the environment.

Both bacteria and fungi are essential for maintaining the balance of ecosystems by recycling nutrients.