Hemangioma is the most common vascular disease in children. Should we treat it aggressively or wait and see? This is a question that parents and even doctors struggle with. To answer this question, we first need to understand the (WWH) What? First we need to determine whether a mass is a hemangioma, a vascular malformation, superficial or deep, mixed? Is it naturally regressing or rapidly proliferating? Then we can decide whether to observe or treat it. For example, around the eyes, it can cause the risk of vision loss, the mouth and nose can cause deformity of the five senses, and the perianal area can cause anal stenosis, which must be actively treated; on the other hand, in the limbs and trunk, it is relatively less harmful. How does it happen? Is it in the growth phase or the receding phase? If it has entered the receding stage and gradually reduced in size, it does not need active treatment; if it is growing rapidly and infiltrating obviously, then it should be treated actively. If the growth is rapid and the infiltration is obvious, active treatment is needed. Then there are children who have formed ulcers, or huge type of tumors, some syndromes, need active treatment. In conclusion Hemangioma needs to be clinically evaluated as early as possible, based on a combination of site, developmental trend, and degree of harm.