paragraph: As water flows through, it causes changes. The flowing water dissolves some types of rock. Some rocks dissolve more easily than others. Over time, the water may dissolve large areas of rocks. With enough time, holes, or caves, can form. Groundwater drips from the ceiling to the floor of a cave. Even deep in the ground, water is still pulled by gravity. This falling water is rich in dissolved minerals. Some of these minerals do not stay dissolved. When this happens, the minerals start to build up. They build up on the ceiling of the cave to create formations called stalactites. A stalactite is a pointed, icicle-like mineral. They form on the ceiling of a cave. They drip to the floor of the cave. It is there the minerals in the water harden to form stalagmites. A stalagmite is a more rounded mineral deposit. It forms on the floor of a cave. Both types of formations grow in size as water keeps dripping and more minerals are deposited. 
question: How are stalactites formed?
answer: When water evaporates in to air