Ceramic composites based either on a particulate, fibre or a lamellar architecture are potentially useful as damage-tolerant high-temperature engineering materials. The ability of the interfaces in such systems to deflect cracks is vital to the damage tolerance of these materials. Transmission electron microscopy techniques enable the chemical and physical characterization of these interfaces, providing information on interlayer thicknesses, chemical species, local bonding and the microstructural features which give rise to the interfacial properties, thereby enabling a full understanding not only of composites after processing, but also after exposure to aggressive environments such as air at high temperature. Examples of the application of transmission electron microscopy to all three composite architectures are described.