This talk will present a class of methods to compute under and over approximating flowpipes for uncertain differential systems, possibly with delays, systems that are pervasive in the modeling of networked control systems. Computing over-approximations of the reachable states has become a classical tool for the safety verification of control systems. Under-approximations are notoriously more difficult to compute, and their use for verification much less studied. I will discuss the guarantees and properties that can be obtained from the joint use of these under and over-approximations for control systems with inputs and disturbances.