Abstract: An apparatus and method for the automated preparation of treated monolayers of sample material, comprising: a centrifuge having a rotor (12) carrying removable chamber blocks (14); sample and reagent dispensers (26) and control systems (20). First, centrifugal force sediments sample material discretely to form a monolayer onto a receiving surface member (32) on one of the chamber blocks (14), while the same centrifugal force opens a valve (48) in the chamber block (14) to drain sample material. Then, centrifugal force delivers sequentially into discrete chamber blocks (14) discrete treating agents, during which time the sampler material monolayer is held in place on the receiving surface member (32) by centrifugal force. Then, each chamber block (14) is drained centrifugally through its already opened valve (48). Each treated sampler material is confined to an individual chamber block (14). Batch and random access delivery of treating agents can be employed.