Lung surfactant is a mixture of 90 wt% lipids and 10 wt% surfactant proteins. The main lipid components are phosphatidylcholines (PC), while phosphatidylglycerols (PG), phosphatidylethanolamines (PE), phosphatidyl inositols (PI), and cholesterol are present in minor amounts. It is well known that the major PC in lung surfactant is dipalmitoyl phosphatidylcholine (DPPC), which accounts for about 40-50 wt% of the total mass, while the remaining PCs are unsaturated. The detailed mechanism by which LS regulates the surface tension in the alveoli is still unclear. DPPC monolayers are the most studied, being the major component and is primarily responsible for reducing the alveolar surface tension to near-zero values at the end of exhalation. The mechanical behavior of phospholipid monolayers is characterized by the surface pressure-area (P-A) isotherm that describes the surface pressure Π = γ 0 -𝛾 𝑚 as a function of the area per lipid 𝑎 𝐿 of the monolayer, where 𝛾 0 is the surface tension of water, and 𝛾 𝑚 is the surface tension of the air-water interface with the monolayer. Additionally, DPPC monolayers undergo 2D phase transitions upon lateral compression. At high 𝑎 𝐿 , the monolayer exhibits a gas (G) phase, where the surfactant molecules are well separated with practically no interactions between them. As the monolayer is compressed and 𝑎 𝐿 decreases, a liquid phase known as the liquid expanded (LE) phase is formed. In the LE phase, the lipid molecules diffuse laterally, with their tails oriented randomly with respect to the surface normal. Further compression results in a solid or gellike phase called the liquid condensed (LC) phase, in which the tails are ordered and oriented along the surface normal. Under specific temperature and surface pressure conditions, these phases can coexist within the monolayer, forming microscopically observable domains with distinct structural and mechanical properties: the LE and LC phases coexist at intermediate values of 𝑎 𝐿 and temperature, characterized by a plateau region in the isotherm, while a coexisting gas phase may appear as holes in the monolayer. This behavior is strongly temperature-dependent; the LE-LC coexistence and the plateau region in the isotherm occur only below the critical point (42°C), near the main transition temperature of DPPC, where the LE and LC phases become indistinguishable. Numerous experimental and computational studies on DPPC monolayers over the past several decades, however, have not provided accurate results due to various limitations. An excellent review on this topic is provided by Stachowicz-Kusnierz et al. As shown in Figure , the experimental data from various groups spread over a wide range at various temperatures. The spread in the experimental data is associated with various experimental difficulties, the experimental apparatus, subphase conditions (such as pH, salinity, and temperature), compression rate, lipid deposition, leakage, impurities, and equilibration time. Accurate experimental isotherms are crucial for developing precise computational models for molecular simulations. The overall trend, shape and behavior of the experimental isotherms in the literature are comparable. However, variations do still exist among the isotherms across different papers. Key characteristic features of DPPC isotherms-including the surface pressure lift-off point, phase transition plateau, and monolayer collapse pressure-show significant variability across different experimental studies, highlighting the need for standardized protocols. These disparities stem from various factors that need to be addressed.