I modeled a heart box with a surprise inside for my girlfriend. 

To print, you also need: 

• 12x neodymium magnets 3x3 mm
• 1x spring 7.5 x 35 mm
• double-sided adhesive tape
• super glue

 I created the model so that it can be used both with a heart inside and as a box itself. I glued the base of the spring with double-sided adhesive tape. I lightly dripped super glue on the spring at the joints with the heart and the base. I also glued the emblem to the top of the box. I connected the hinges of the box with a piece of filament and sealed the filament on both sides.

 I printed all parts except the bottom box without supports, because the hinges have a smaller overhang. 

The holes for the magnets have a 0.2 tolerance, so it is better to glue them with super glue as well. 

I printed smaller parts like the heart and the spring base at a slow speed of about 30mm/s and cooled it a lot. 

I hope someone will like the model and it will make their loved one happy on Valentine's Day.