Inspired by a paper by Prandtl, a simple explanation for the occurrence and the character of the surface tension in liquids is devised, which connects a molecular view with a continuum model of the liquid. Doing so, the nature of the so-called surface tension can be understood as an imbalance between internal pressure and cohesive forces related to (virtual) cut surfaces orthogonal to the liquid’s surface. By including these cohesive forces as part of the stress tensor, a non-isotropic stress tensor is obtained close to the surface.