The photo sequence in the upper image shows, left to right, a fluid-filled tube falling under gravity, impacting a rigid surface, and rebounding upward. During free-fall, the fluid wets the sides of the tube, creating a hemispherical meniscus. After impact, the surface curvature reverses dramatically to form an intense jet. If, on the other hand, the tube is treated so that it is hydrophobic, the contact angle between the liquid and the tube will be 90 degrees during free-fall, impact, and rebound, as shown in the lower image sequence. The liquid simply falls and rebounds alongside the tube, without any deformation of the air-liquid interface. (Photo credit: A. Antkowiak et al.)