Lyophilized.

Freeze-dried for stability.

Lyophilization, commonly called freeze-drying, removes water from a preparation by freezing it and then lowering the pressure so the ice turns directly to vapour without passing through a liquid phase. Because it avoids heat, it preserves molecules that would be damaged by conventional drying, which is why it is the standard way peptides are supplied. Water is what enables most of the chemical reactions that degrade a peptide over time, so removing it dramatically extends shelf life and makes a product stable enough to ship and store. The visible result is the cake or powder in the vial, and its appearance is not entirely cosmetic: a collapsed, discoloured, or oily cake can indicate a process or storage problem. Lyophilized material is typically stored cold and protected from moisture, and vials are usually sealed under vacuum or inert gas, which is why a vial can appear to contain almost nothing. Two clarifications matter. The visible bulk is often mostly excipient, meaning bulking agents and buffers, rather than peptide, so cake size says little about content. And freeze-drying is a stability process, not a purification or sterilization process: it preserves whatever was in the vial, including impurities and contamination.