If you have left a vehicle parked in a wooded area for a few days you may have had this problem. For the past year and a half, I have had 4 or 5 separate incidents of mice taking up residence in the car. This problem is obviously so gross and also scary because mice can wreck your car by chewing on the wiring. I also have the eternal fear of one scampering across my foot while driving.
There are lots of ideas for dealing with mice in the car, from playing loud music to placing a scary garden gnome with big eyes near where you park. Obviously you could use traps, but some people (like me) are too squeamish to deal with the aftermath of that. Peppermint oil is a good option because while it is nontoxic to humans, mice are very sensitive to it. Apparently, they won't go near it. I put some drops of peppermint essential oil (extract doesn't work) on cotton balls and put them around the car. I suspect this would work in say, kitchen drawers, if you have a mice populations in your house. It does not stop them from nesting, but it will keep them away!
In addition to the peppermint oil, I have driven the car more frequently and I don't live in the woods anymore - and I have had no more mouse problems since July.