A multi-well assembly according to one embodiment comprises a multi-well block and a guide plate. The multi-well block defines a plurality of wells, with each well having a fluid-impermeable bottom surface. The guide plate defines a plurality of fluid passageways corresponding to the wells of the multi-well block. The guide plate is configured such that, whenever the guide plate is registered with the multi-well block, fluid communication is established between each well and an associated fluid passageway. The guide plate enables iterative chemical or biological processes using multiple multi-well blocks. A seal plate is configured to cut fluid communication conferred by the guide plate via registration with the guide plate, or via registration with the multi-well block (once the guide plate is removed). The seal plate allows iterative chemical or biological processes within a single multi-well block.