Abstract: An electrophoresis device for use in separating a mixture of analytes in a fluid sample is provided, the device comprising a first dimension separation medium through which the analytes may migrate, the separation medium being carried on one face of a flexible sheet, the surface area of that face being greater than that of the region of contact between the separation medium and the sheet, wherein the first dimension separation medium is located within a first separation zone which is defined at least partly by the flexible sheet, the device further comprising a fluid chamber, separated from the first dimension separation zone by the flexible sheet, in which fluid may be retained in contact with that face of the sheet opposite to the face on which the separation medium is carried. The device may additionally comprise a second separation zone, in which a second separation medium may be located, in order to carry out a second dimension electrophoretic separation.