Abstract: A device (1) for laying down particles, for example, cells, on a substrate for subsequent examination thereof comprises a porous substrate (117) and delivery means for delivering to the porous substrate (117) a sample of fluid that contains the particles, the delivery means comprising an inlet (6, 7a, 7b, 7c) for the fluid, and a passageway (11) extending along a first direction from the inlet towards the porous substrate (117), the passageway (11) being so arranged that it permits flow of the fluid generally along a first direction towards the substrate (117) whilst further permitting spreading of then fluid in a direction transverse to the first direction.