The history of kidney biopsy as an invasive test is not long, just more than half a century since its appearance, and in the early 1950s, two Danish physicians, Iversen and Bran, first used percutaneous renal puncture technique for the diagnosis of kidney disease patients, creating a new era of kidney biopsy pathology diagnosis. Of course, the biopsy technique at that time was very primitive, due to the limitation of the equipment, only the location of the kidney could be vaguely determined under the X-ray machine and punctured, as you can imagine, the efficiency of the biopsy at that time was very low, accompanied by high complications of the biopsy, and even carried out under direct vision kidney biopsy, which is actually equivalent to obtaining kidney tissue under open surgery. At great cost, scientists are not discouraged because what is gained is a diagnosis of kidney disease and a leap in the understanding of the pathogenesis. Also not discouraged were scientists in many fields, all working together, for more than half a century, with the continuous development of immunology, immunopathology and electron microscopy techniques, especially the commercialization of antibodies for the detection of various immunoglobulins, complement, fibrin (fibrinogen) and other components (such as hepatitis B virus antigen, type III collagen, etc.) deposited in kidney tissue, the invention of ultrasound and the development of the rapid biopsy technique, the greatly improved safety of the kidney puncture technique, the percutaneous kidney puncture technique has become an important means of clinical diagnosis of kidney disease, and the resulting kidney biopsy pathology has become a new branch of modern pathology. With kidney biopsy technology, it is equivalent to having the golden eye to understand what happened to the kidney in the past, what state it is in now, and where it will go in the future! To borrow a common saying, we can “know 500 years before, and count 500 years after”. Kidney biopsy pathology occupies a very important position in the knowledge framework of modern kidney disease, it is the cornerstone of kidney disease diagnosis, the diagnosis of most kidney diseases need to rely on kidney biopsy pathology to provide information. It is also an important basis for the development of kidney disease treatment plans. Similarly, for transplanted kidneys, transplantation biopsy pathology also has a very important position. For clinical symptoms such as elevated creatinine, proteinuria and hematuria after kidney transplantation, it is necessary to identify the specific cause and make a diagnosis with the help of transplant kidney biopsy. It can be said that with the help of biopsy pathology, we can distinguish between creatinine elevation, proteinuria and hematuria which are clinically very similar. For the common rejection after transplantation alone, the transplanted kidney biopsy can subdivide the rejection into cellular rejection, humoral rejection, antibody-mediated rejection and slow rejection, and only after the diagnosis is subdivided can the corresponding therapeutic measures be targeted. In addition to rejection, the diagnosis of recurrent glomerular disease in the transplanted kidney and post-transplant neoplastic glomerulonephritis requires the basis of transplant kidney pathology. After understanding the importance of transplant kidney biopsy, we need to understand the timing of transplant kidney biopsy. When is the most appropriate time to receive a transplant kidney biopsy? Many people use transplant kidney biopsy as a measure of last resort and only consider it when the transplanted kidney is significantly impaired. This is a very wrong view. For lesions, it is always the earlier the lesion is diagnosed the sooner it can be treated correctly and with good results. Especially in kidney disease, the course of the disease is often long and the clinical symptoms can often be stable over a long period of time, but if you look at it only from the clinical presentation, it is easy to be confused and lose your vigilance. I do not know that kidney disease is sometimes calm on the surface, but in fact, the dark current, and when the shocking waves appear, there is nothing that can be done. Therefore, it is important to undergo biopsy as soon as clinical symptoms appear in order to unravel the phenomenon and see the essence. Not only is the presence of clinical symptoms an indication for biopsy of the transplanted kidney, but we even emphasize the importance of routine biopsy. In fact, many patients who underwent routine biopsy found problems, corrected the diagnosis, improved the treatment plan, and ultimately benefited from the transplanted kidney. Some of you may ask, what if you start with empirical treatment and then undergo biopsy if it doesn’t work? In fact, we all should know the truth that a difference of a thousand miles. It is not that empirical treatment is not accurate, but it is difficult to achieve accuracy. Empirical treatment is often almost accurate, or 90% accurate, but it is important to know that the difference of 10% combined with the long course of the disease, the final destination may be far from the same.