A container for keeping contents in separate compartments (C1, C2) before use, the container comprising: - a first container body providing a first compartment for containing a first content, the first container body having an end and a first outer side wall extending around the first compartment; - a second container body separate from the first container body, the second container body providing a second compartment for containing a second content, the second container body having a second outer side wall extending around the second compartment, and an end opposite to the end of the first container body; - an interface device, separate from the first container body and separate from the second container body, for connecting the first container body to the second container body; - an internal passage, allowing communication between the first compartment and the second compartment; - a closure member sealing the internal passage, the closure member comprising an intercompartment membrane separating the first compartment from the second compartment; wherein the interface device comprises a first connector and a second connector each of annular shape and engaged with each other to provide a connection between the first compartment and the second compartment, wherein the first connector comprises a ring part fastened to an annular end of the first container body, the second connector being fastened to an annular end of the second container body and being provided with opening means, and wherein the opening means of the second connector is movable relative to the first connector, so as to move between a position distal from the internal passage sealed by the closure member and an activated position to open the internal passage by opening the intercompartment membrane, allowing mixing between the first content and the second content, characterised in that the second connector comprises a retaining element, the first connector being provided with a detent element (31 b) configured to engage with the retaining element so as to prevent the second connector from being detached from the first connector. - a first container body providing a first compartment for containing a first content, the first container body having an end and a first outer side wall extending around the first compartment; - a second container body separate from the first container body, the second container body providing a second compartment for containing a second content, the second container body having a second outer side wall extending around the second compartment, and an end opposite to the end of the first container body; - an interface device, separate from the first container body and separate from the second container body, for connecting the first container body to the second container body; - an internal passage, allowing communication between the first compartment and the second compartment; - a closure member sealing the internal passage, the closure member comprising an intercompartment membrane separating the first compartment from the second compartment; wherein the interface device comprises a first connector and a second connector each of annular shape and engaged with each other to provide a connection between the first compartment and the second compartment, wherein the first connector comprises a ring part fastened to an annular end of the first container body, the second connector being fastened to an annular end of the second container body and being provided with opening means, and wherein the opening means of the second connector is movable relative to the first connector, so as to move between a position distal from the internal passage sealed by the closure member and an activated position to open the internal passage by opening the intercompartment membrane, allowing mixing between the first content and the second content, characterised in that the second connector comprises a retaining element, the first connector being provided with a detent element (31 b) configured to engage with the retaining element so as to prevent the second connector from being detached from the first connector.