In 1995 the genesis of stabilized methods was established by Professor Hughes from the standpoint of the variational multiscale theory (VMS). By splitting the solution into resolved and unresolved scales, it was unveiled that stabilized methods take into account an approximation of the unresolved scales or error into the finite element solution. In this work, the VMS theory is exploited to formulate an explicit a-posteriori error estimator, consistent with the assumptions inherent to stabilized methods.The proposed technology, which is especially suited for fluid flow problems, is very economical and can be implemented in standard finite element codes. It has been shown that, in practice, the method is robust uniformly from the diffusive to the hyperbolic limit.The success of the method can be explained by the fact that in stabilized methods the element local problems for the fine-scale Green's function capture most of the error and the error intrinsic time-scales are an approximation to the solution of the dual problem. Applications to the Euler and linear elasticity equations are shown.