  New X-ray and neutron diffraction experiments have been performed on
ethanol-water mixtures as a function of decreasing temperature, so that such
diffraction data are now available over the entire composition range. Extensive
molecular dynamics simulations show that the all-atom interatomic potentials
applied are adequate for gaining insight of the hydrogen bonded network
structure, as well as of its changes on cooling. Various tools have been
exploited for revealing details concerning hydrogen bonding, like determining
H-bond acceptor and donor sites, calculating cluster size distributions and
cluster topologies, as well as computing the Laplace spectra and fractal
dimensions of the networks. It is found that 5-membered hydrogen bonded cycles
are dominant up to an ethanol content of 70% at room temperature, above which
concentration ring structures nearly disappear. Percolation has been given
special attention, so that it could be shown that at low temperature, close to
the freezing point even the mixture with 90% ethanol possesses a 3D percolating
network. Moreover, the water sub-network also percolates even at room
temperature, with a percolation transition occurring around 50% ethanol.

Soft Condensed Matter