Fat grafting has suddenly become popular in China in recent years, and fat grafting for breast augmentation has become a recent trend in the plastic surgery industry. For the currently popular fat transplantation breast augmentation, let us explain in detail. The process of fat transplantation for breast augmentation The patient’s own excess fat is sucked out to obtain fat cells, purified to get purified fat cells (CAL+), and then injected into the recipient area of the breast evenly in different levels to make it viable. Obtaining fat The clinical use of negative pressure liposuction to obtain fat cells is common. Fat purification No matter how the fat cells are obtained, they need to be purified to remove blood and oil to obtain purified fat (CAL+) for soft tissue filler injection. The most common methods of purification used in the clinic are filtration, gravitational sedimentation and centrifugation. Among these methods, filtration is not suitable for filler injections because it yields only clumped fat cells rather than multichanneled microscopic fat cells. Comparison of gravity sedimentation and centrifugation shows that the gravity sedimentation group has a higher number of viable cells, but contains a large number of blood cells and a lower number of stem cells, while the centrifugation group can better separate the blood residue and has a higher proportion of stem cells, but the ability of fat cell viability decreases linearly as the centrifugation speed increases. Common donor areas for fat sources Abdomen (upper abdomen, lower abdomen), thighs (outer thighs, inner thighs), waist and near the knees. Of these, the lower abdomen and inner thigh areas have the highest concentration of fat stem cells and are the best areas for fat source supply. Injection Methods Clinically, single-channel injection of large amounts of fat is ineffective and overfilling may increase the probability of complications (fat necrosis, secondary calcification and even severe infection). The permanent survival of fat can be significantly improved by a multi-channel, multi-level injection technique using a blunt-tipped injection needle injected in a fan-like, flat pattern and injected as the needle is withdrawn, allowing the fat grafts to come into better contact with blood-supplied tissues. This is because according to Poisseuille’s law, the larger the diameter of the injection needle, the greater the pressure on the fat cells in the recipient area. When injecting with a 20-22 gauge needle, morphologic changes in fat cells in the syringe were observed, and it is possible that the changes in cell morphology may decrease the percentage of viable cells; however, there was no fat cell morphology with a 16-18 gauge. Therefore, the use of a small needle increases the number of viable cells in the recipient area. Grafted fat initially relies on the plasma at the margins of the blood-supplying tissues for nourishment, and can only survive for long periods of time if it is vascularized, so smaller grafts are more likely to survive, and the survival rate depends on the thickness and geometry of the area in which the grafts are inserted; the percentage of viable grafts decreases progressively as the thickness of the grafts increases. Fat implanted in the superficial muscle layer survives better than that implanted subcutaneously or submuscularly, analyzed as the rich blood supply and loose space on the muscle surface provide conditions for the survival of fat cells. Adipose Stem Cells & Plasma Growth Factor Stem cells are primitive cells with self-replicating and multidirectional differentiation potential, which can be differentiated into multiple functional cells or tissues and organs under certain conditions. Freshly isolated adipose stem cells mixed with donor fat grafts can significantly improve the survival rate of transplanted fat. Differentiation of adipose stem cells into adipocytes is the production of growth factors, which may be the underlying principle. Plasma growth factors are platelet-rich, highly concentrated plasma made from one’s own blood that accelerates tissue repair and promotes vascular growth.PRP includes EGF epidermal growth factor, FGF fibrotic northwestern growth factor, VEGF vascular endothelial growth factor, TGF transforming factor, and PDGF platelet-derived growth factor. The use of PRP did significantly improve the survival of the transplanted fat. Conclusion Liposuction with multi-channel, multi-level fat injection usually results in satisfactory and reliable clinical outcomes. For now, facial fillers are one of the relatively safe routes of application. And it remains to be seen whether fat grafting for breast augmentation is the mainstream direction for the future or has some risks.