What size do particles behave like waves?

[AJI]

The famous double slit experiment.
Use large particles and fire them at two holes large enough for them to pass through and you simply get two lines behind the holes where they hit. (Marbles for example).
But use small enough particles through small holes and you get them behaving like waves. (Electrons for example - as long as you are not observing them on their journey that is).

My question is, what is the dimension for when large enough becomes small enough to make the transition between particle behaviour and in to wave behaviour?

[AJI]

Cheers.
Interesting read.

So it seems it can be done with relatively large molecules as well as single electrons, protons etc.