Citizen Scientists—individuals in the general public attentive to science-based investigation and communication—engage in studies that can supplement efforts by credentialed scientists.

The U.S. Forest Service has characterized citizen science as:

". . . the collection of scientific data by individuals who are not professional scientists. They are prepared for their work as citizen scientists by professional biologists from the land management agency. These projects are on-going and consist of a network of volunteers. Citizen Science networks are very important. The citizen science monitoring programs would not be the success it is without the participation of citizen scientists."

Many citizen scientists are involved in monitoring (in particular, environmental monitoring). Another important component of monitoring science involves biological monitoring or biomonitoring. Biomonitoring is done for humans as well as for wildlife (plant and animal).