Why does phospolids face outwards and the tails face inward?

Phospholipids have a hydrophilic (water-attracting) "head" and two hydrophobic (water-repelling) "tails." In an aqueous environment, the heads face outward towards the water, while the tails face inward, away from it. This arrangement forms a bilayer that creates a stable barrier, allowing cells to maintain distinct internal and external environments. This structure is fundamental to cell membranes, enabling the selective permeability essential for cellular function.