What causes Capillarity?

Hint: Capillarity is the rise or depression of a liquid in a very small passage like a tube of small cross-sectional area, just like the spaces between the fibers of a towel or the openings during a porous material. Capillarity isn't limited to the vertical direction. Water is drawn into the fibers of a towel, in spite of how the towel is oriented.

Complete answer:
Capillarity occurs due to intermolecular forces between the liquid and surrounding solid surfaces. If the diameter of the tube is sufficiently small, then the combination of physical phenomenon (which is caused by cohesion within the liquid) and adhesive forces between the liquid and container wall act to propel the liquid. capillary action or capillarity is caused when the adhesive force is stronger than the cohesive force. Cohesive force is the force between the water molecules. Adhesive force is that the force between the water molecules and therefore the walls of the vessels.
Capillarity is that the results of surface, or interfacial, forces. The rise of water in a very thin tube inserted in water is caused by forces of attraction between the molecules of water and therefore the glass walls and among the molecules of water themselves. These attractive forces balance the force of gravity of the column of water that has risen to a height. The narrower the bore of the capillary, the upper the water rises

Note:
Liquids that rise up in bore tubes inserted into the liquid are said to wet the tube, whereas liquids that are depressed within thin tubes below the surface of the surrounding liquid don't wet the tube. Water is a liquid that wets glass capillary tubes; mercury is one that doesn't. When wetting doesn't occur, capillarity doesn't occur.