The lectures that four authors present in this volume investigate core topics related to the accelerated expansion of the Universe. Accelerated expansion occured in the very early Universe - an exponential expansion in the inflationary period 10^(-36)s after the Big Bang. This well-established theoretical concept had first been proposed in 1980 by Alan Guth to account for the homogeneity and isotropy of the observable universe, and simultaneously by Alexei Starobinski. and has since then been developed by many authors in great theoretical detail.