Watching outside while under a carpet cloak of invisibility.

We demonstrate in this work a unique approach for watching outside while hiding in a carpet cloaking based on transformation optics. Unlike conventional carpet cloaking, which screens all the incident electromagnetic waves, we break the cloak and allow incident light get into the carpet. Hence outside information is detected inside the cloak. To recover the invisible cloaking, complementary techniques are applied in the broken space. Consequently, a hiding-inside and watching-outside (HIWO) carpet cloak is sewed, which works as an invisible cloaking and allows surveillance of the outside at the same time. Our work provides a strategy for an ideal cloak with "hiding" and "watching" functions simultaneously.