Establishing boundaries is a dynamic process and it involves the way the (m)other is met as different. When she is present for him physically and emotionally the infant can both discover his distinction without trauma and explore the object as exciting in itself and as stimulating new possibilities. This is a complex process that continues to resolve itself through creative engagement with life. I shall briefly survey some of the literature on establishing a body identity and on ‘mechanisms’ of interaction and consider the way in which they contribute to boundary experience.