1 : Take a White paper and write a message using lemon water ( example : “Happy Valentine Day” as a message).
2 : Write another message down to first message using black ink. (Second Message :: “Hold this paper on heat”).
3 : Rounded the message-paper and put it in bottle with colorful heart shape made from colorful chart paper.
4 : So, when another person open that white-paper and only read second message so his\her put that paper on heat source and Get first message “Happy Valentine Day”.