The Meaning of Anatta - Stages of insight knowledge

If someone at this moment would clearly know the characteristic of the reality which experiences an object, as an element which experiences, he would have attained already the first stage of insight knowledge, the “defining of nama and rupa.” One cannot develop panna immediately to the degree of insight that is the fifth stage of “Principal Insight,” “knowledge of dispassion” (nibbida nana). After the first stage of insight panna has to be developed further so that it can directly understand conditions for the realities that arise. The second stage of insight is “discerning conditions for nama and rupa” (paccaya-pariggaha-nana).
Then panna can be developed further to the degree of realizing the arising and falling away of realities in succession. This is the third stage of insight, "comprehension by groups” (sammasana nana).
After that panna should be developed to the degree of realizing the arising and falling away of one reality at a time, separately. This is the first stage of “principal insight” (mahavipassana), “knowledge of the arising and falling away of nama and rupa” (udayabbaya nana). 
After that panna must be developed further so that it can penetrate more the impermanence of realities that fall away all the time. This is the second stage of principal insight, “knowledge of dissolution” (bhanga nana). Then panna must be developed still further to the stage of seeing more clearly the danger and disadvantage of the falling away of realities. This is the third stage of principal insight, “knowledge of appearance as terror” (bhaya nana). After that the fourth stage can be realized, which is “knowledge of danger” (adinava nana). After that panna, should be developed to the degree of the fifth stage of insight, “knowledge of dispassion” (nibbida nana). After that several more stages of insight have to be reached before enlightenment can be attained.