A mould and tissue cassette for automated embedding of tissue, and a method of operation are disclosed. The mould attaches to the cassette prior to embedding, and fits into a rack. The rack supports the mould holding the tissue cassette when the mould and cassette are in a first position. When the mould and cassette are moved to a second position, a projection on the rack separates the mould from the cassette, to facilitate easy removal. Also disclosed is a mould for a tissue cassette having projections for holding the mould to a rack, so that the tissue cassette is not in contact with the mould.