Without seeing the material, I can only guess and given the description you have given, I would say mice. Look through all your drawers for more signs. Check areas in you kitchen where you store food material such as cereals and other dried goods.
Look in areas where you store towels or other items which they might find useful for a nest.
Set traps. Wear gloves so human odors do not get on the traps. Mice are not all that smart but can learn. Use peanut butter on the traps and place in the areas where you find the droppings. If you have mice, you should catch at least one.
If you have a cat or dog in the house, they sometimes will catch and/or scare the mice enough for them to leave if they are normally out door mice. If they are house mice, they may find ways to stay. Dogs will usually smell them and start exploring and possibly indicating more areas where the mice have been. If you check the areas out, you will probably see more dropping.
If you have a cat, it might begin to leave you gifts of whole or parts of the mice it catches. Some cats, by their behavior, may also indicate areas where mice are present. Some indoor cats have no idea and may not be very effective. If you have an outdoor cat, it will most likely be helpful with the problem.
If the droppings are an eighth of an inch or larger, you have rats, not mice. They are big enough that you may start to see things spilled or large holes in boxes of food. They are much more intelligent and cautious so trapping them will be more difficult and you may need a professional to come in to deal with the problem. When cornered, they will fight back against a cat or dog so it will depend on the pet's experience in succeeding with getting the rats.