Understanding the origins of the Universe and how it works and evolves is the present mission of a large community of physicists. It calls for a large scale vision, involving general relativity, astrophysics, and cosmology. Theoretical physics is presently at an important moment in its history. As predicted by Einstein, gravitational waves have been experimentally proven to exist. With the discovery of the Higgs boson, the set of interactions and elementary particles that is called the "standard model" (SM), is complete. Yet the Higgs boson itself, and how it breaks the electroweak symmetry, remains a fascinating subject requiring further studies and verification. Furthermore, several experimental facts are not accounted for by the SM: (i) the baryon asymmetry of the Universe, (ii) the nature and origin of dark matter, and (iii) the origin of neutrino masses; these have no unique, if any, explanation in the SM and yet will require answers from particle physics. We need to explore further both SM and its extensions. This is a subject of papers included in this book, which gives representation to the topics discussed during the Matter to the Deepest conference in 2019 in Poland (http://indico.if.us.edu.pl/event/5).

The International Conference on Theoretical Physics, TH-2002, took place in Paris from July 22 to 27 in the Conference Center of the UNESCO, the United Nations Educational Scientific and Cultural Organization, under aegis of the IUPAP, the International Union of Pure and Applied Physics and of the French and Euro pean Physical Societies, with a large support of several French, European and international Institutions. International and crossdisciplinary, TH-2002 welcomed around 1200 partic ipants representing all domains of modern theoretical physics. The conference offered a high-level scientific program, including 18 plenary lectures, 45 general lectures in thematic sessions and 140 more specialized lectures, partly invited and partly selected among proposals received from participants. Around 500 contribu tions were also presented as posters. Plenary lectures as well as general thematic lectures were addressed to a general audience of theoricians, not only to specialists. According to our commitments towards UNESCO and other sponsoring insti tutions, TH-2002 attributed more than 200 fellowships, mostly to scientists from developing countries and Eastern Europe, covering registration fees and, for more than half of them, stay expenses with student type accomodation. Special highlights of the conference included • the opening ceremony on July 22, with the participation of Mrs Claudie Haignere, French Minister of Research, and M. Walter Erdelen, General Ad joint Director for Sciences at UNESCO. Their opening addresses were espe cially appreciated and are reproduced below. This ceremony preceded the first lecture by Professor Cohen-Tannoudji, Physics Nobel prize winner.

Considers the extensions of agreements concerning nuclear power with Australia, Colombia, Japan, Philippines, Denmark, Ireland, Norway, Greece, and the Republic of South Africa.

Dark matter in the Universe has become one of the most exciting and central fields of astrophysics, particle physics and cosmology. The lectures and talks in this book emphasize the experimental and theoretical status and perspectives of the ongoing search for dark matter, and the future potential of the field into the next millennium, stressing in particular the interplay between astro- and particle physics.