In attempting to reduce the size of functional devices, the thickness of polymer. films has reached values even smaller than the diameter of the unperturbed molecule. However, despite enormous efforts for more than a decade(1), our understanding of the origin of some puzzling properties of such thin. films is still not satisfactory and several peculiar observations remain mysterious. For example, under certain conditions, such. films show negative expansion coefficients(2 - 6) or show undesirable rupture although energetically they are expected to be stable(7). Here, we demonstrate that many of these extraordinary effects can be related to residual stresses within the. film, resulting from the preparation of these. films from solution by fast evaporation of the solvent(8). Consequently, depending on thermal history and ageing time, such. films show significant changes even in the glassy state(9,10), which we quantify by dewetting experiments and corresponding theoretical studies. Identifying the relevance of frozen- in polymer conformations gives us a handle for manipulating and controlling properties of nanometric thin polymer. films.