Lead halide perovskite (LHP) nanocrystals (NCs) have attracted significant attention due to their unique optical properties, high photoluminescence quantum yields, and facile synthesis. Unlike conventional semiconductor NCs, LHP NCs have a "soft" and predominantly ionic lattice, making them highly tolerant to structural defects and surface states. This unique property allows for a wide range of applications in optoelectronics, single-photon sources, and photovoltaics. LHP NCs can be synthesized using various methods, including ligand-assisted hot-injection, re-precipitation, microwave-assisted synthesis, and solution-based approaches. Their high ionic character enables rapid synthesis at room temperature, and they exhibit excellent stability in solution, although they are prone to structural changes upon isolation and purification. LHP NCs are highly defect-tolerant, which is attributed to their unique electronic structure and dynamic lattice. This defect tolerance allows for high photoluminescence quantum yields without the need for surface passivation. However, LHP NCs face challenges related to their structural instability, which can lead to changes in shape and crystallinity. Strategies to stabilize LHP NCs include the use of dielectric shells, compositionally matched salts, and matrix-encapsulation in inorganic materials. Additionally, post-synthetic transformations such as anion and cation exchange enable the tuning of optical properties and the creation of new functional materials. LHP NCs have shown great promise in optoelectronic applications, including light-emitting diodes (LEDs), solar cells, and single-photon sources. They exhibit high photoluminescence quantum yields, narrow emission linewidths, and tunable emission wavelengths, making them suitable for display technologies, lighting, and quantum communication. However, the use of lead in LHP NCs raises concerns about toxicity, prompting research into lead-free alternatives. While lead-free perovskites such as tin and germanium-based materials have been explored, they often exhibit lower stability and performance compared to LHP NCs. Despite these challenges, LHP NCs remain a promising area of research due to their unique properties and potential applications. Ongoing studies aim to improve the stability, scalability, and environmental safety of LHP NCs, while exploring new compositions and structures to enhance their performance in various applications. The development of efficient, stable, and environmentally friendly LHP NCs is crucial for their widespread adoption in consumer electronics and quantum technologies.Lead halide perovskite (LHP) nanocrystals (NCs) have attracted significant attention due to their unique optical properties, high photoluminescence quantum yields, and facile synthesis. Unlike conventional semiconductor NCs, LHP NCs have a "soft" and predominantly ionic lattice, making them highly tolerant to structural defects and surface states. This unique property allows for a wide range of applications in optoelectronics, single-photon sources, and photovoltaics. LHP NCs can be synthesized using various methods, including ligand-assisted hot-injection, re-precipitation, microwave-assisted synthesis, and solution-based approaches. Their high ionic character enables rapid synthesis at room temperature, and they exhibit excellent stability in solution, although they are prone to structural changes upon isolation and purification. LHP NCs are highly defect-tolerant, which is attributed to their unique electronic structure and dynamic lattice. This defect tolerance allows for high photoluminescence quantum yields without the need for surface passivation. However, LHP NCs face challenges related to their structural instability, which can lead to changes in shape and crystallinity. Strategies to stabilize LHP NCs include the use of dielectric shells, compositionally matched salts, and matrix-encapsulation in inorganic materials. Additionally, post-synthetic transformations such as anion and cation exchange enable the tuning of optical properties and the creation of new functional materials. LHP NCs have shown great promise in optoelectronic applications, including light-emitting diodes (LEDs), solar cells, and single-photon sources. They exhibit high photoluminescence quantum yields, narrow emission linewidths, and tunable emission wavelengths, making them suitable for display technologies, lighting, and quantum communication. However, the use of lead in LHP NCs raises concerns about toxicity, prompting research into lead-free alternatives. While lead-free perovskites such as tin and germanium-based materials have been explored, they often exhibit lower stability and performance compared to LHP NCs. Despite these challenges, LHP NCs remain a promising area of research due to their unique properties and potential applications. Ongoing studies aim to improve the stability, scalability, and environmental safety of LHP NCs, while exploring new compositions and structures to enhance their performance in various applications. The development of efficient, stable, and environmentally friendly LHP NCs is crucial for their widespread adoption in consumer electronics and quantum technologies.