It explodes with love! Watch the video for the how-to:
This is a technique I learned a hundred years ago on Two Peas in a Bucket (a site now sadly defunct) and I can't remember the original source. However, a commenter on YouTube told me that this fold is actually a well known fold called "Turkish Map Fold." Sure enough, I did a quick google search and found lots of great written instructions with diagrams. Here's my favorite.
Of course, while this card is intended for Valentine's Day, the idea works for any holiday! Give it a try, it's super easy and the explosion always makes the recipient smile!