For crystalline materials, atomistic local structures are deviations from their long-range average crystal structures. With the recent development of experimental techniques and in-depth investigation methods for probing local structures, it has been realized and understood that local structures have profound influences on the physical properties of functional materials, and the understanding of local structures provides theoretical instructions for the improvements of materials performances as well as development of novel applications. This review summarized the well-established X-ray and neutron scattering techniques, data analysis and model refinements mothods in the local-structure investigation researches; in addition, examples of local structural investigations for several classical ferroelectric perovskites are reviewed.