A second argument in this direction was given by several astronomers in the 1950's. It had long been known from the double peaked emission lines observed in the nebulae, that they were expanding. The velocity of expansion is on the average 15 to 20 km s -t, with only exceptional cases differing by more than a factor 2 from this value. Since this nebular material presumably escaped from the central star, the question was asked: which stars have an escape velocity of the order of 20 km s-t? The answer is Red Giants. On considering this answer, other reasons for its correctness became apparent. A red giant actually has the characteristics of an early stage of a PN. Much of its mass is present in a high density core which could easily be the forerunner of the PN central star. Some of its mass is present in the enormous giant atmosphere which could easily become the nebula. It only remained to set the giant atmosphere in motion at the escape velocity. The solution the star has chosen to solve this problem is not yet completely understood. It is clear however that the mass lost by the star to form a PN occurs at a stage prior to its being observed as a PN. Thus the previous stage, whether OH/IR star, Mira variables and other types of red giants will also be discussed.