This book is derived from the conference entitled 'Algae and extreme environments - Ecology and Physiology' held in Trebon, Czech Republic, September 11-16, 2000. At the conference, 28 lectures and 46 posters were presented. All together 75 persons from 17 nations participated in the conference. The aim of the conference was firstly to bring together research phycologists for discussions concerning prokaryotic and eukaryotic oxyphototrophic micro-organisms living in extreme environments, and secondly to map the present state of knowledge within this research topic. The volume starts with origin and evolution of life on Earth and covers also possibilities of life in extraterrestrial worlds. The opening part (Sektion I) introduced by editors is followed by all the most commonly studied stress factors and responses across a broad range of extreme environments and/or marginal ecological situations.