Cosmology has not been the subject matter of a Saas-Fee Advanced Course since 1978. That occasion was the memorable course entitled Observational Cosmologyy with lecturers J.E. Gunn, M.S. Longair, and M.J. Rees. A new course on cosmology seemed overdue, and we subsequently planned and or ganized, with the endorsement of the Swiss Society of Astrophysics and As tronomy, the present, 23"^^ Saas-Fee Advanced Course. Probing (drilling) the Universe to greatest depths, in terms of diffuse radiation and discrete objects, with all consequences for our understanding of cosmic evolution, was meant to be the unifying aspect of this course. Hence the title The Deep Universe. We are very happy to have won such competent and brilliant scientists as lecturers. Malcolm Longair - Saas-Fee lecturer for the second time! - lectured on cosmological background radiation ("The Physics of Background Radia tion"); Richard Kron on observations of extremely distant galaxies ("Evo lution in the Galaxy Population"); while the Grand Master of Cosmology, Allan Sandage, provided the fundaments of it all, also in a historical sense ("Practical Cosmology: Inventing the Past"). The course took place from 29 March to 3 April, 1993, in Les Diablerets, with around 90 participants. The format was as usual, every lecturer giving 9 or 10 lectures of 45 minutes.