BACKGROUND: The indications for fat grafting are increasing steadily. In microfat grafting, thin injection cannulas are used. The authors describe their experience of fat injection with even thinner injection needles up to 27 gauge. The fat used for this purpose is processed into "nanofat." Clinical applications are described. Preliminary results of a study, set up to determine the cellular contents of nanofat, are presented. METHODS: Nanofat grafting was performed in 67 cases to correct superficial rhytides, scars, and dark lower eyelids. Three clinical cases are described. In the research study, three fat samples were analyzed. The first sample was a classic lipoaspirate (macrofat). The second sample was microfat, harvested with a multiport small-hole cannula. The third was microfat processed into nanofat. Processing consisted of emulsification and filtering of the lipoaspirate. Fat samples were analyzed for adipocyte viability. Cells from the stromal vascular fraction and the CD34+ subfraction were quantified. The stem cell quality was investigated by culturing the cells in standard and adipogenic media. RESULTS: No viable adipocytes were observed in the nanofat sample. Adipose-derived stem cells were still richly present in the nanofat sample. Cell cultures showed an equal proliferation and differentiation capacity of the stem cells from the three samples. Clinical applications showed remarkable improvements in skin quality 6 months postoperatively. No infections, fat cysts, granulomas, or other unwanted side effects were observed. CONCLUSIONS: Nanofat injections might become a new concept in the lipofilling area. In clinical situations, nanofat seems to be suitable for skin rejuvenation purposes.