Fine-grained soil, also known as loess (5 letters), is a type of soil composed of small particles that are less than 0.002 millimeters in diameter. It is usually formed by the accumulation of wind-blown silt and clay particles. Loess is highly erodible and can be found in many parts of the world, including China, Europe, and North America. It is often used in agriculture due to its high fertility and water retention capacity.