The crystallisation of macromolecules is largely dependent on the generation of supersaturation while also maintaining conditions that minimally disrupt their natural molecular conformation in solution. While conventional methods of generating supersaturation typically involve either lowering the temperature of the crystallisation solution or allowing solution evaporation to increase concentration, this is often unsuccessful in obtaining macromolecular crystals. This is because their flexible nature necessitates relatively higher energy to overcome the thermodynamic barrier to nucleation. Seeding presents itself as an innovative approach to mitigate this energy barrier and generate high-quality macromolecular crystals. This method involves utilising either macromolecular crystalline seeds, dissolved additives (soft templates), or undissolved additives (hard templates). The underlying principles of these methods primarily rely on three fundamental mechanisms: functional group matching, epitaxy, and topographical effects, all of which are extensively discussed in this chapter. Over the past two decades, there has been a significant enhancement in the success of macromolecular crystallisation, largely attributed to advancements in seeding and templating strategies. This chapter provides a comprehensive summary of the research conducted on seeding and templating to enhance the crystallisation capabilities of macromolecules, as well as the development of purification protocols for these intricate systems.