**1. Introduction**

Many procedures have been described throughout history in an attempt to increase lost tissue volume: dermo-fat grafts, omental free flaps, and musculoskeletal flaps, to name a few.

The history of autologous fat transfer began in Europe with Neuber presenting his first fat transfer work at the 22nd Congress of the German Society of Surgery in 1893 [1], followed by Mojallal [2], Lexer [3], and Rehn [4] who described its use in a variety of procedures including thoracic and abdominal surgeries, breast surgeries and the field of neurosurgery and orthopedics, within the so-called "open-air" era - before liposuction (1889–1977).

Brunning was the first, in 1911, to inject fat into the subcutaneous tissue for augmentation [5]. This technique continued to be promoted as an alternative to resolve depressive areas. Without a doubt, its incorporation into the field of plastic surgery is where it has had its maximum development.

The first attempts consisted of excising fatty tissue and placing it in small pockets in the subcutaneous layer. In the 50s, Peer observed that by placing small portions, at least 50% of their initial volume was lost in the long term and that this would depend mainly on early anastomosis of the recipient and donor vasculature, thus describing the theory of survival of fatty tissue grafts. It was established that the number of viable adipocytes at the time of graft placement directly correlates with the final volume that survives [6].

The concept of absorption of fat grafts began practically from the moment of its use. Due to this, throughout its development, different theories arose that tried to explain what happened with transplanted fat [7, 8].

For some time, fat transfer lost popularity. This led to the search for other alternatives, such as silicone, polymers, and hydroxyapatite crystals. It was in 1980 with the appearance of liposuction when the trend of obtaining fat for grafting was renewed [9]. From our perspective, we consider that different stages have contributed to the boom in autologous fat transfer in the field of cosmetic and reconstructive surgery. Ironically, during the development and refinement of liposuction techniques, the collected fat was thrown away. The question soon arose, *why not use it in other areas of the body to provide volume and solve depressions?*

In 1986, Fournier [10] and Illouz [11] presented modifications in the technique for obtaining fat through aspiration syringes. Coleman in 1994 introduced his technique, perfectly describing the steps for sampling, purification by centrifugation, and transfer (reinjection), which he later called: Lipostructure®, warning that any traumatic act to obtain fat should be avoided, thus dividing the times: "unpurified" (With the discovery of liposuction 1977–1994), and "purified or atraumatic" (after the descriptions of Roger Coleman from 1994 to date). The literature has described that fat tissue grafts can cause a lasting correction; however, it has also been documented that fat undergoes multiple manipulations in its reinjection process, which affects its survival [12].

Verderame described that the surgeon had to compensate for this "shrinkage" by transplanting a greater amount of fat than required, hoping that the initial desired result with this "overcorrection" would equalize with subsequent reabsorption [13].

This natural evolution on the improvement of the liposuction technique included improvements in equipment (suction machines and cannulas) and scientific bases to better understand the metabolism of adipocytes, their viability, and performance, and permanence over time [14–16].

There are reports in the literature that compare the benefits of centrifugation, decantation, and washing of fat tissue, in an attempt to ensure the best viability of adipocytes and, therefore, better permanence.

In a recent systematic review, Zhou et al. evaluated graft survival based on technique. The authors reported a statistically significantly higher facial fat graft survival rate of 71% in the cell-assisted lipotransfer group compared to 52% in the control group (standard fat grafting) [17].

From the beginning of stem cells obtained from adipose tissue, their potential therapeutic use was already envisioned at the level of tissue engineering and cell biology [18]. Matsumoto et al. in 2006, [19] described a technique called cellassisted transfer (CAL). This technique consists of autologous transplantation of adipocytes enriched with stem cells derived from fatty tissue. Enzyme digestion is achieved using collagenase. With favorable culture media and different centrifugation steps, the stromal vascular fraction (SVF) is obtained. The SVF contains; stromal cells, endothelial progenitor cells, preadipocytes, ASCs, etc. In an adipogenic environment, ASCs can directly differentiate into adipocytes and contribute to volumetric restoration. They also promote graft survival through angiogenesis and the release of growth factors [20]. Yoshimura [21] described the use of this technique in cases of facial lipoatrophy and post-reconstruction breast augmentation and described the technique for obtaining the ASCs.

The current use of fat transfer to replace volume or camouflage soft tissues is an increasingly popular method in plastic surgery, especially in craniofacial surgery. Due to our current globalized and increasingly competitive environment, it is undeniable that in the field of esthetic surgery, volumetric lipoinjection with adipose stem cells as facial profiling or combined with facial rejuvenation surgical procedures has great acceptance.
