https://www.cutoutandkeep.net/projects/heart-stencil-on-a-t-shirt • Posted by ivona.
Find a picture of heart anatomy and print it. Cut it to get a stencil (it's much easier if you use a scalpel).
Place the stencil on the shirt and fix it with pin needles.
paint it. (don't forget to put a plastic bag or something inside the shirt to protect the back side of the shirt)
wait until the paint is dry,and be proud of yourself :D