This chapter provides guidance on the inspection of injections for visible particles. The terms "particle," "particulates," and "particulate matter" are equivalent and do not have different meanings when used in this chapter. Particulate matter is defined in Particulate Matter in Injections 〈788〉 as “extraneous mobile undissolved particles, other than gas bubbles, unintentionally present in the solutions.” Visual inspection is a probabilistic process, and the specific detection probability observed for a given product for visible particles will vary with differences in dosage form, particle characteristics (such as size, shape, color, and density), and container design. Some products and packages limit the ability to inspect for particles when compared to clear solutions in transparent containers. Additional guidance when inspecting these difficult-to-inspect products (DIP) are provided later within this chapter.