A foam and pre-foam production process, and a foam and a pre-foam is described. The process comprises the steps of: forming a pre-foam composition comprising oil(s), thermoplastic elastomer(s) and heat expandable thermoplastic particles encapsulating heat expandable gas or liquified gas, the said particles being present in an amount which provides the required foam cell density. A heat treating step for the said composition to cause the particles to expand and produce a foam from the said composition is also described.