  One of the most questionable issues in wetting is the vertical force balance
that is excluded in Young's law. On soft deformable solids, such as biotic
materials and synthetic polymers, the vertical force of liquid leads to a
microscopic protrusion of the contact line, i.e. a "wetting ridge". The wetting
principle that determines the geometry of the ridge-tip is at the heart of the
issues over the past half century. Here, we reveal a universal wetting
principle by directly visualizing ridge-tips with high spatio-temporal
resolution using x-ray microscopy. We find that the tip-geometry is asymmetric
and bent, and invariant during ridge growth or by surface softness. This
singular geometry is explained by linking the macroscopic and microscopic
contact angles to Young's and Neumann's laws, respectively. Our dual-scale
model would be applicable to a general framework in wetting and give new clues
to various issues in cell-substrate interaction and elasto-capillary problems.
