The Book of Shadows — in the attic.
Reading an incantation from it, she unwittingly set in motion events that fulfilled an ancient prophecy. Strange and harrowing occurrences began which eventually led the sisters to realize that they are witches.
They discovered that not only do they possess supernatural powers, they come from a long line of powerful witches. The first in the line, Melinda Warren, was burned at the stake in the Salem Witch Trials.
However, before she died, Melinda prophesied that each coming generation of Warren (later Halliwell) witches would grow stronger and stronger, culminating in the arrival of three sisters -- the strongest good witches the world had ever seen; the three sisters would form The Power of Three, the most powerful magical force ever.
Prue Halliwell, the oldest sister, developed the power of telekinesis where she could move things with her mind, later gaining the power of astral projection, where she could essentially make a clone of herself appear wherever she desired.
Piper, the middle child, was initially given the power to freeze molecules, later developing the power to blow things up: molecular combustion.
Phoebe, the youngest sister, had the original power of premonition, at first being able to see future events and later past events as well, and often is used to reveal the truth. She later obtained the power to levitate which let her defy gravity for several seconds which was useful with her martial arts skills; in addition, her empathic powers developed in later years where she could read the feelings and emotions of others.
After the tragic death of Prue, it was revealed that the sisters had a younger half-sister named Paige, born to their mother Patty and Sam, her Whitelighter, a guardian angel for witches.
As such a relationship was forbidden and unheard of at the time, the baby was given to a nun and later adopted by the Matthews family. Her birth parents requested only that her first name begin with
