Lipid droplets (LDs) are intracellular organelles found in most cells, playing key roles in metabolism by storing energy and membrane lipids. They function as an oil-in-water emulsion, with a phospholipid monolayer at the interface that stabilizes them. LDs are crucial for energy storage, membrane synthesis, and maintaining cell homeostasis. They are involved in various diseases, including obesity and atherosclerosis, and have applications in biofuel production. LDs are stabilized by phospholipids and proteins that reduce surface tension and increase elasticity. However, they are metastable and can destabilize through processes like coalescence and Ostwald ripening. Coalescence involves the merging of LDs, while Ostwald ripening leads to the disappearance of smaller droplets. These processes are influenced by surface tension, line tension, and the composition of lipids and proteins on the LD surface. Proteins interact with the LD monolayer surface, with some targeting through amphipathic α-helices or hydrophobic hairpins. These proteins play roles in lipid metabolism, membrane dynamics, and LD remodeling. LD formation originates from the endoplasmic reticulum (ER) and involves the budding of lipid droplets from bilayer membranes. The size and stability of LDs depend on factors such as phospholipid composition, surface tension, and the presence of specific enzymes. LDs can shrink through lipolysis, where lipases break down triglycerides and sterol esters. This process is regulated by proteins like perilipin1 and CGI-58, which control access to the LD core. Autophagy also contributes to LD turnover by targeting LDs for degradation. Additionally, LDs serve as platforms for storing hydrophobic proteins and lipid intermediates, and they may play roles in drug delivery and viral assembly. Understanding LD biology through the lens of emulsion science and biophysics is essential for elucidating their functions and roles in health and disease. Advances in this field are expanding our knowledge of LDs and their impact on cellular processes.Lipid droplets (LDs) are intracellular organelles found in most cells, playing key roles in metabolism by storing energy and membrane lipids. They function as an oil-in-water emulsion, with a phospholipid monolayer at the interface that stabilizes them. LDs are crucial for energy storage, membrane synthesis, and maintaining cell homeostasis. They are involved in various diseases, including obesity and atherosclerosis, and have applications in biofuel production. LDs are stabilized by phospholipids and proteins that reduce surface tension and increase elasticity. However, they are metastable and can destabilize through processes like coalescence and Ostwald ripening. Coalescence involves the merging of LDs, while Ostwald ripening leads to the disappearance of smaller droplets. These processes are influenced by surface tension, line tension, and the composition of lipids and proteins on the LD surface. Proteins interact with the LD monolayer surface, with some targeting through amphipathic α-helices or hydrophobic hairpins. These proteins play roles in lipid metabolism, membrane dynamics, and LD remodeling. LD formation originates from the endoplasmic reticulum (ER) and involves the budding of lipid droplets from bilayer membranes. The size and stability of LDs depend on factors such as phospholipid composition, surface tension, and the presence of specific enzymes. LDs can shrink through lipolysis, where lipases break down triglycerides and sterol esters. This process is regulated by proteins like perilipin1 and CGI-58, which control access to the LD core. Autophagy also contributes to LD turnover by targeting LDs for degradation. Additionally, LDs serve as platforms for storing hydrophobic proteins and lipid intermediates, and they may play roles in drug delivery and viral assembly. Understanding LD biology through the lens of emulsion science and biophysics is essential for elucidating their functions and roles in health and disease. Advances in this field are expanding our knowledge of LDs and their impact on cellular processes.