Works best on a printer with good resolution to allow the hearts to slide freely when printed. Mine slide right away once the brim is removed. I printed the pendant at 0.2 mm layer height with an outer brim to keep the small pieces in place. I set the fill pattern to “concentric” for the top and bottom layers. A color change in the last two layers (0.4mm) gives the small hearts and the large heart outline a nice “pop” of color.

Update: Just added a 50% scale version (TinyDancingHeartsPendant.stl) that will be tricky to print, but worked for me with the following settings: 

• 0.08mm layer height
• inner and outer brim - with 1mm brim width
• concentric fill pattern for top/bottom layers