![Close up of some Earthworms in soil.](http://static.sciencelearn.org.nz/images/images/000/001/867/full/Earthworms20160902-3334-414xqk.jpg?1674167002)
Earthworms help break down organic matter into soil and are an important indicator of the health of the soil. They can also be used directly as a ‘tool’ to determine if certain toxins are present, by measuring the timing of their response to a touch.