Consider an ideal blackbody. Let us assume that there are enough electronic levels in the body so it can absorb radiation at all wavelengths. (This was discussed in an earlier question) While most real materials are only approximately black bodies as absorbers they are black body emitters to a very good approximation.
The key factor about emission of blackbody radiation is not merely that it emits at all wavelengths but that the intensity of the resultant radiation follows a universal curve. So how does this happen? Is it to be understood in apology with single particle interference? In that situation each electron merely has a probability of reaching any point of the screen. After a large number of electrons teach the screen one gets an interference pattern. Does each emitter constituting the blackbody have a probability of emitting at any particular wavelength? But here we have a macroscopic body. Even more interesting is the experimental proof that the universe is itself a blackbody emitting at 2.7K!