The term "dust grains" refers to tiny particles or specks of matter that make up dust. These small particles can be composed of various materials, including soil, pollen, cosmic dust, and other debris. Dust grains are often suspended in the air and can cause problems such as allergies or respiratory issues when they become airborne. In astronomy, "dust grains" specifically refer to tiny particles of interstellar matter that exist between stars and can be made up of elements like carbon, silicon, and oxygen. These dust grains play an important role in the formation of new stars by providing a medium for gravitational collapse.