Planetesimals are small celestial bodies that formed in the early stages of the formation of planets in our solar system. These bodies are typically several kilometers in diameter and are thought to be the building blocks of planets. Planetesimals are believed to have formed from the material left over after the formation of the sun and were important in the process of planet formation through accretion and collisions. Studying planetesimals can provide valuable insights into the early history of our solar system and the processes that led to the formation of planets.