Capillarity is a crucial and pervasive phenomenon in nature and has found important applications in wearable electronics, medical devices, and miniature energy systems. Capillary tubes are the transport vessels in which the surface wettability plays an essential role in efficient and accurate liquid delivery. However, it remains a challenging issue to tailor and measure the surface wettability inside the tubes in view of the confined space. Herein, recent progress on the surface science under confined space is discussed, with a particular focus on surface modification, wettability evaluation, and advanced applications of the superwetting capillary tubes. This Perspective aims to highlight the emerging opportunities in surface science with spatial confinement toward flexible and portable devices.