• Cellular and molecular control hair cell regeneration in non-mammalian species (in particular zebrafish and chickens) • Our current understanding of the capacity for hair cell replacement in mammals (rodents and humans). • Signals controlling pro-regenerative behaviors in supporting cells, the hair cell progenitors. • New techniques that have been applied to study the genetic and epigenetic regulation of hair cell regeneration in mammals and non-mammals. • Contributions of stem cells toward building new tools to explore how hair cell regeneration is controlled and toward developing cells and tissue for therapeutic transplantation. • Studies that have applied gene and drug therapy to promote regeneration in mammals.