Pleckstrin homology (PH) domains are protein structural motifs that play a crucial role in cellular signaling and membrane interactions. They are typically around 100 amino acids long and are known for their ability to bind phosphoinositides, which are lipid molecules found in cell membranes. This binding helps proteins localize to specific membrane sites, influencing various cellular processes. PH domains are found in a wide range of proteins, including those involved in cell signaling, cytoskeletal organization, and vesicle trafficking. Their ability to interact with different phosphoinositides allows for diverse functions, making them essential for maintaining cellular functions and responding to environmental signals.