A system and method for storage and retrieval are provided. The system includes a multi-level storage structure, and mobile robots configured to pick, transport and place one or more tote, container, or object. This system and method can be used in order-fulfillment applications in which one or more workstations accommodate a picker that transports one or more eaches from a tote on one of the autonomous mobile robots to a put location, and an input/output interface induct material into the system and discharge fulfilled orders from the system. The mobile robots are further configured to move from level to level in the multi-level storage structure via inclined or vertical tracks without requiring a vertical lift or vertical conveyor.