The emergence of order from disorder is a common theme in nature—the formation of cell membranes from phospholipids, the crystallization of water molecules into snowflakes, and the intertwining of DNA strands into helices are just a few examples. The term “self-assembly” refers to the spontaneous formation of an ordered structure or pattern from its initially disordered components without any human intervention (Whitesides and Grzybowski, 2002). In particular, self-assembly provides a promising bottom-up route to three-dimensional (3D) structures. In the context of programming self-assembly, which requires encoding the information of the target structure into the building blocks, colloidal particles are especially attractive building blocks because of the scope for tuning the interparticle interactions (Cademartiri and Bishop, 2015; Glotzer and Solomon, 2007; Whitesides and Boncheva, 2002). In recent years, the availability of a rich arsenal of colloidal building blocks, thanks to advances in synthetic methods, has paved the way for an exotic variety of self-assembled structures. However, understanding the physical principles, which govern the self-assembly of these building blocks, holds the key to programming self-assembly into target structures. In the present chapter, we discuss synthetic methods for Janus and multipatch colloidal particles and their self-assembly behavior, largely targeted for open crystals, which have appealing applications as photonic crystals as well as phononic and mechanical metamaterials (Aryana and Zanjani, 2018; Joannopoulos, 1997; Mao and Lubensky, 2018).