It's been suggested a lot that this be added to Scratch. Frankly, I don't think it'll be happening in the extremely near future simply because it'd be really hard to implement this in a way that's easy to understand like the rest of Scratch.
However, I believe the Scratch Team have mentioned that this is a feature they plan to include in future versions of Scratch.
Offline
Coolstuff got it right. For now, you can use Mesh (Here's a guide), which works okay.
Offline