Here's why:

* Water seeps through cracks in the cave ceiling. This water often contains dissolved minerals like calcium carbonate.

* As the water drips from the ceiling, it evaporates. This leaves behind a tiny deposit of minerals.

* Over time, these mineral deposits build up, forming a long, icicle-shaped structure. This is the stalactite.

Stalactites are like upside-down icicles, growing downwards from the ceiling. Stalagmites, on the other hand, are the mineral formations that grow upwards from the cave floor, often directly below a stalactite.