A Square glass disk is used to foretell the future. A playing card is selected from a deck of cards. 
The spectator thinks of the card and then breathes onto the crystal. 
The image of the selected card appears on the surface of the glass!, then it slowly fades.

Another variety is more popular and insteresting. 
If you love someone but are shy to tell your mind,this trick is absolutely what you need. 
Tell your lover that you have something to say.
Let him or her breathe onto the crystal.
The words of "I LOVE YOU" appears on the surface of the glass!, then it slowly fades.
Now he or she knows your heart. 
The whole product is complete with clothbag, ghost glass,and instruction paper. 
Simple operation and easy to go. As long as you can breathe, you can do this trick.