The part of soil that comes from living things is called humus.

Here's how it works:

* Decomposition: When plants and animals die, they decompose. This means bacteria, fungi, and other organisms break down the dead organic matter.

* Humus Formation: The decomposition process produces a dark, crumbly material called humus. Humus is rich in nutrients and helps improve soil structure, water retention, and aeration.

So, while soil is made up of different components like minerals, sand, silt, and clay, humus is the part that directly originates from living things.