At the edge of galaxies, in the lowest surface brightness regimes, lies the boundary where gas can collapse to form new stars. These regions remain largely unexplored due to the lack of very deep images that allow us to characterize the star-forming clumps at the edge of the discs. In this sense, we do not know whether stellar activity in these

In this talk we will discuss host galaxy observations of Fast X-ray Transients (FXTs). FXTs are minute-to-hours long flashes of X-rays, discovered serendipitously in X-ray satellite data (mainly Chandra and XMM-Newton) and they have been associated with energetic extra-galactic phenomena. However, their exact nature has not yet been established

The Hubble and James Webb Space Telescopes, with their outstanding depth and spatial resolution, are opening up the possibility of studying the edges of disk galaxies over a significant cosmic time interval. This allows us to study in detail the evolution of galaxy edges over the past 8 Gyr. The edge of galaxies, understood here as the farthest