The human hair follicle is a dynamic structure that generates hair through a complex and exquisitely regulated cycle of growth and remodelling governed by numerous genes. Hair growth occurs in unsynchronized cycles consisting of three phases: anagen (growth phase), catagen (shortening phase) and telogen (resting phase).Domashenko and colleagues1xEfficient delivery of transgenes to human hair follicle progenitor cells using topical lipoplex. Domashenko, A. et al. Nat. Biotechnol. 2000; 18: 420–423Crossref | PubMed | Scopus (104)See all References1 have shown that topical application of a lipososme–DNA mixture (lipoplex) to mouse skin and to human skin xenografts on mice results in the selective transfection of follicle matrix cells, predominantly keratinocytes, in the outer root sheath. In vivo transfection is most efficient at the onset of anagen when the follicle progenitor cells are proliferating. Onset of the growth phase can be induced by depilation of the hair and application of retinoic acid to the grafts before liposome application, leading to almost 50% transfection efficiency.These results provide a starting point for the successful targeting of specific genes to hair-follicle progenitor cells to treat diseases of the hair and skin using topical lipoplexes. The specific introduction of genes into growing follicles to induce hair growth would provide an effective remedy for common baldness and alopecia areata, which affects 1–4% of the population. Alternatively, altering the characteristics of the progenitor cells could induce transient changes in hair colour, strength or thickness.