A method of operating chromatography column apparatus comprising a column tube (101) and first and second discrete end cell structures, associated with the respective ends of the column tube and positionable to close off the column tube and define therein a column space for retaining chromatography medium in use of the apparatus. The first end cell portion comprises a piston portion (106) fitting slidably in the column tube. The column tube and the second end cell structure are separated to provide an access spacing between them. The piston portion (106) of the first end cell structure is advanced through the column tube to expose it at the open second end of the column tube, for maintenance of the piston portion thus exposed. Corresponding chromatography apparatus is another aspect of the disclosure.