The outside of our brain is surrounded by a thick layer of cranial bone that provides good protection. When there are various neurological pathologies that require surgical treatment, the first thing we need to do is to open the skull. Obviously without opening the skull we can’t see the brain and we can’t treat it surgically, but how much? This is the question that neurosurgeons need to consider. In the 1940s and 1950s, the common surgical approach was still to operate under the naked eye. Since 1968, when neurosurgeons began to apply microscopes in surgery, more than 40 years ago, neurosurgery has gradually developed into the minimally invasive era, which means that most neurosurgery is done under a microscope, and the operation is very delicate, plus today’s preoperative imaging and intraoperative navigation technology have been able to accurately locate the lesion location, so the scope of opening the bone is getting smaller and smaller, more and more The patient’s entire damage is also reduced to a minimum. So even though it is called craniotomy, the area of the skull flap that we open is actually around 6-175px in diameter, depending on the type and size of the lesion, and some surgeries can even be done with a 50px diameter hole in the skull. Except in one case, when we have to decompress a swollen brain, we do a larger area of skull resection to minimize the intracranial pressure and save lives.