Recent progress in experimental investigations, related to the determinant variables of the L-H transition, is reviewed in this paper. In particular, it is put forward that the `wall effect', which often produces spurious contributions to the various parametric dependences of the H-mode threshold power, may be an embodiment of the atomic processes, involving the edge neutrals as a `hidden' variable. In addition, relations between the edge plasma quantities and threshold scaling are emphasized, quoting the ostensibly different observations in various tokamaks.