To evaluate the in vivo effect of hUMSCs‐Exos in treating vitiligo, and to compare the therapeutic efficacy of 2D‐Exos and 3D‐Exos, a melanoma‐Treg‐induced vitiligo mouse model that recapitulated the pathological characteristic of human patients with vitiligo was established as previously described (Figure 3A).[19] Flow cytometry analysis revealed nearly complete elimination of CD4+ T cells in peripheral blood of the mice after injection of CD4 antibody (Figure S1A, Supporting Information). Here, CD4 is linked to melanoma.