This document discusses surface tension, which is the contractive tendency of a liquid's surface that allows it to resist external forces. Surface tension is caused by cohesive forces among liquid molecules, which pull inward on molecules at the surface. This creates internal pressure and forces liquid surfaces to contract to a minimal area, pulling droplets into a spherical shape. Some examples of how surface tension is exhibited include insects floating on water, paperclips floating, water beading on leaves, and water droplets forming spheres.