# Periphery

- [IonInvariants](/devs/smart-contract-architecture/periphery/ioninvariants.md)
- [IonLens](/devs/smart-contract-architecture/periphery/ionlens.md)
- [IlkSlot0](/devs/smart-contract-architecture/periphery/ilkslot0.md)
- [IonRegistry](/devs/smart-contract-architecture/periphery/ionregistry.md)