I'm not deeply trained in Physics at all. But Einstein's theory about Brownian motion kind of moves me.

"
If ρ(x,t) is the density of Brownian particles at point x at time t, then ρ satisfies the diffusion equation: 

 

where D is the mass diffusivity.
" 

http://en.wikipedia.org/wiki/Brownian_motion#Einstein.27s_Theory