Distribution of the pores in a 60×60×150 grid at 10 K (left), 60 K (middle), and 100 K (right). The temperature is initially set at 10 K, and is increased at a rate of 2 K/min to mimic laboratory conditions. Each dot shows an empty space with a tag n (colour scale) corresponding to the number of empty cells in a radius n around the cell n. This figure is the negative image of Fig. 3.