Mikko Laine had PhD 1994 in Helsinki, was postdoc in Helsinki, Heidelberg, and CERN, and professor of theoretical physics in Bielefeld 2003-2012 and Bern 2012-today. He has published over 150 scientific articles, mostly on thermal field theory and particle cosmology. Mikko Laine is a co-author of the book "Basics of thermal field theory" (Springer, 2016).Simona Procacci had PhD 2023 in Bern, and a postdoc in Geneva 2023-today. She has published close to 10 scientific articles on inflationary cosmology, cosmological phase transitions, and gravitational wave physics. Simona Procacci got the faculty prize for the best PhD thesis in physics at the University of Bern in 2023, which served as an inspiration for this book.