Think of water of crystallization like bricks embedded in a specific architectural blueprint; removing or adding them changes the structural stability and form of the entire crystal, just like Epsom salt crystals lose their water and turn into a powdery anhydrous form when strongly heated.

Remember 'Epsom Seven' to recall that Epsom salt contains 7 molecules of water.

Water of crystallization refers to the fixed number of water molecules chemically bound in a definite stoichiometric ratio within a crystalline compound. In magnesium sulfate heptahydrate ($MgSO_4 \cdot 7H_2O$), these seven water molecules contribute to the crystal lattice structure and stability of the solid salt under standard conditions.

Memorize the common water of crystallization values for frequent exam compounds like Blue Vitriol ($CuSO_4 \cdot 5H_2O$), Green Vitriol ($FeSO_4 \cdot 7H_2O$), and Washing Soda ($Na_2CO_3 \cdot 10H_2O$).