1. What is a baby hair pen? Baby fetal hair brush is a kind of brush made from newborn fetal hair. Its production process is unique and requires multiple processes. Because the lanugo hair is soft and tough, the brush made from it is soft and delicate and has excellent writing effect. 2. The historical origin of fetal hair brushes As early as the Tang Dynasty, some people began to use fetal hair to make brushes. The emperor and nobles at that time