Mold needs a damp environment to grow. When it dries out, the outer layer of cells shrivels up and die. Without that moist environment, mold cannot fulfill its lifecycle by expressing its functions for reproduction and spreading. However, inside your home, there are many ways for mold to find moisture - such as high humidity or excessive wood rotting. These environments will allow the mold to thrive despite drying out on the surface of their colonies. The best way to fight against pesky molds is prevention--to increase floor ventilation with air conditioning or ceiling fans, since this reduces humidity caused by bathing or cooking indoors.