Although the Standard Model has been remarkably successful in enhancing our understanding of the elementary structure of matter and in accurately describing all observed particle physics processes to date, as noted in the previous chapter, there remain a number of unanswered questions. For example, the Standard Model does not explain why we observe only matter in the Universe but no or nearly no antimatter. Furthermore, the particles of the Standard Model are not sufficient to build up all the components of the Universe. To explain the nature of dark matter, we need at least one further particle beyond those of the Standard Model. Extensions of the theory designed to address these unresolved questions must be experimentally testable. It is an exciting challenge to search for observable effects that could confirm these well-motivated theoretical ideas. In this chapter, we explore several experimental searches for particles, decays or other effects that arise from extensions of the Standard Model. If any of these experiments were to detect the predicted effects, it would provide a significant indication of the direction in which the theory should be further developed