• Nucleation control is crucial for achieving wafer-scale 2D single crystals, with strategies focusing on density and position.
• Controlling nucleation density enables growth from a single nucleus, leading to large-area single crystals.
• Controlling nucleation position facilitates unidirectional island alignment and seamless stitching, essential for single-crystal films.
• The review provides strategic pathways for the growth of emerging 2D materials, highlighting future directions.