Scientists tackle a solution of scientific problems together with their experience, knowledge, methods and skills which were successful in the past and it is undeniable that these all take part on formation of conjectures and assumptions. The sleep or more precisely one of the phase of sleep (REM-sleep) undoubtedly plays the role in the process in which we create a conjectures and assumptions. We do not know all about but I claim that during the REM-sleep we probably choose from a conjectures and assumptions from which the hypothesis of the first line are emerged. Only after breaking through the barrier of observativness we can mobilize all form of thinking. I do not claim that every problem will be solved but merely that we have managed to put to use more of our own thinking equipment. There are several methods of unblocking actual thinking and bringing into play endoceptively formed structures and I claim that most profitable is the REM-sleep which still permits the preservation of the integrity of thinking. We must learn to maintain our conscious between vigilance and dream in the state which reflects our processes of thinking but still retains a single theme, and in which, if necessary, we can still by an act of will come back to the starting point of our thought.