Small electric fields (EFs) can direct cell growth and migration in vitro. But, although similar EFs occur in developing embryos and near to healing wounds, no-one has shown that they have a physiological effect at the single-cell level in vivo. On p. 4681, Song et al. remedy this situation by showing that nerve regeneration and wound healing are stimulated and directed by an endogenously generated EF in wounded rat cornea. In the corneal epithelium, normal ion movements establish a transcorneal potential difference (TCPD) of about 40 mV. When wounded, the corneal epithelium instantaneously short-circuits and the TCPD drops to zero at the wound site, setting up a lateral endogenous EF in the epithelium. The authors show that drugs that increase the TCPD (and consequently the EF produced after corneal wounding) enhance the extent and direction of nerve sprouting and the rate of epithelial wound healing; drugs that reduce the TCPD have the opposite effect. These results have clinical implications for both wound healing and nerve regeneration.