In the Timaeus, Plato is thought to identify the 'receptacle' with primordial matter, and calls it the 'wet nurse of all becoming'.
The receptacle is the wet nurse of all becoming. This means it takes on the characteristics of whatever comes into it.
"My description here is extremely minimal. The shimmer of ecologi- cal pulses arises also in their intersecting and crosscutting ripples, for example, the work of the sun ensures that rain does not take over the earth, and the work of rain ensures that the sun does not take over; their pulse is complementary, and each part arrives as relief from an excess of the other. There are winds, of course, and the play of winds on grasses and on clouds. The effect, if one is attentive, is an iridescence or shimmer sparking up at these larger scales."