organizational culture three levels Schein

According to Schein and his 3 levels of organizational
culture number 3 is really giving me a difficult time. Explain the 3 level of
Underlying assumptions – This level deals with phenomena that remain
unexplained when insiders are asked about the values of the organizational
culture. Information is gathered in this level by observing behavior carefully
to gather underlying assumptions because they are sometimes taken for granted
and not recognized. According to Schein, the essence of organizational culture
lies in this level.