Surface Tension and air pressure trick
Components: a jar, a card, a net (onion net), toothpicks and water.
When the card is removed the water stays in the jar because the molecules of water are joined together, like a thin membrane between each hole in the net.
Even though the membrane is broken with a toothpick, it is generated again and again..
Air Pressure: The air pressure is pushing upward harder than the water is pushing downward.
Surface Tension: http://en.wikipedia.org/wiki/Surface_Tension Surface tension is caused by the attraction between the molecules of the liquid by intermolecular forces.