Deep observations made with the MUSE spectrograph on ESO’s Very Large Telescope have uncovered vast cosmic reservoirs of atomic hydrogen surrounding distant galaxies. The exquisite sensitivity of MUSE allowed for direct observations of dim clouds of hydrogen glowing with Lyman-alpha emission in the early Universe -- revealing that almost the whole night sky is invisibly aglow.The video is available in 4K UHD.The ESOcast Light is a series of short videos bringing you the wonders of the Universe in bite-sized pieces. The ESOcast Light episodes will not be replacing the standard, longer ESOcasts, but complement them with current astronomy news and images in ESO press releases.More information and download options: http://www.eso.org/public/videos/eso1832a/Subscribe to ESOcast in iTunes! https://itunes.apple.com/podcast/esocast-hd/id295471183?mt=2Receive future episodes on YouTube by pressing the Subscribe button above or follow us on Vimeo: https://vimeo.com/esoastronomyWatch more ESOcast episodes: http://www.eso.org/public/videos/archive/category/esocast/Find out how to view and contribute subtitles for the ESOcast in multiple languages, or translate this video on YouTube: http://www.eso.org/public/outreach/partnerships/translators/Credit:ESODirected by: Nico Bartmann.Editing: Nico Bartmann.Web and technical support: Mathias André and Raquel Yumi Shida.Written by: Ivana Kurecic and Calum Turner.Music: written and performed by Stan Dart (www.stan-dart.com).Footage and photos: ESO, F. Kamphues, Digitized Sky Survey 2, Lutz Wisotzki et al, MUSE Consortium, R. Bacon and J. Pérez.Executive producer: Lars Lindberg Christensen.