This talk will present a class of methods to compute under and over approximating flowpipes for differential systems, possibly with delays, systems that are pervasive in the modeling 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. We 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.