High resolution transmission electron microscopy has been used to probe the microstructure of the n = 2 Ruddlesden-Popper manganates Sr{sub 2}LnMn{sub 2}O{sub 7} (Ln = Y, La, Nd, Eu, Ho). Intergrowths of n = 1 (K{sub 2}NiF{sub 4}) are observed only for Ln = La. Intergrowths with n {ge} 5, essentially perovskite microdomains, are seen in the other compositions. The density of perovskite regions is greatest near the edges of the thin specimens, with the n = 2 structure becoming established in the bulk. The complementarity of HRTEM and neutron diffraction is discussed.