System for preparing and making available a flowable medium that is formed by mixing a dry substance with a fluid. A system for preparing and making available a flowable medium (43) that is formed by mixing a dry substance (39) with a fluid (41), in particular a medium for therapeutic purposes, comprises the following system components: a) a first container (1), which receives the fluid (41) and has a wall part (3) that is able to deform counter to a restoring force in order to change the container volume； b) a second container (35) receiving the dry substance (39), and c) a transfer device (21) for producing a fluid communication between the first container (1) and the second container (35).
