Last week I made this origami heart. Here's a step by step instructions to make a 3D origami heart.
The below picture shows how to fold triangles - Golden venture Folding
From an A4 size paper, 32 such pieces can be made.
I used around 200 pieces - made from A4 printed paper which I colored red using crayons.
From step 1 to 5, keep on adding pieces, increasing one piece with each level as shown.
In step 6, leave the center while keep adding pieces on either side. So in total you will be adding 6 pieces.
After this level, you need to add 6 pieces at every level, till it forms a shape as shown in picture.
Step 10 is quite tricky, insert the open ends on right side marked 1,2,3 into the pockets on left side marked 1,2,3. If your pieces are coming out, stick them with a glue.
After that press the module in shape.
Click on the image for better view
For more - check out my FB page The Art of folding a Paper