As a reader of this book you will become familiar with current, up-to-date comprehensive knowledge about all classes of eukaryotic algae, the cyanobacteria, and symbiotic interactions of algae and cyanobacteria with other organisms. For example, the lichens are symbiotic consortia and a prominent example of a particularly successful 'evolution by cooperation'. We expand even to the beginnings of terrestrial plant life and the bryophytes, which are gradually transmitting to the vascular plants. We collectively call this enormous phylogenetic wealth of photoautotrophic organisms the 'new cryptogams', abandoning the traditional definition of cryptogams. The new cryptogams are all those autotrophic organisms that share being hydro-passive, meaning that they are unable of controlling water uptake or release, in contrast to vascular plants. While being basal of and phylogenetically much more diverse than the vascular plants, the new cryptogams are ecologically highly relevant in all ecosystems of our Planet. They are responsible for more than half of the Earth's annual oxygen production.