Graphical programming or modeling environments in which a preview window of an object is provided are disclosed. The preview window may be provided when the pointer of a pointing device hovers over an object and automatically disappear when the pointer of the pointing device is placed out of a predetermined region relating to the object. The object can be hierarchical so that the object includes a subsystem. Another preview window may be provided when the pointer of the pointing device hovers over the subsystem and automatically disappear when the pointer of the pointing device is placed out of a predetermined region relating to the subsystem. The subsystem of the object may also include another subsystem.