The estimate for the number of existing microbial species is 105 -- 106, but only some thousands have been isolated in pure culture and described. The principal reason for this gigantic disparity is that, mysteriously, over 99% of all environmental microorganisms refuse to grow in the laboratory. The phenomenon of microbial uncultivability has been recognized as one of the main challenges for basic and applied microbiology and finding a way to access this uncultivated microbial majority may change many aspects of biology and biotechnology as we know them today. This volume presents the discovery of the phenomenon, the current hypotheses on its molecular nature, state-of-the-art approaches of "outsmarting" the uncultivated microorganisms and the principal applications of the new insights into medicine and biotechnology. Hopefully, it will be the key to the hidden universe of uncultivated microorganisms, their unparallel diversity and enormous applied potential.