The ejection of matter and the radiation field from the luminous late stages of stellar evolution form the shape and the physical conditions of the ISM. This causes giant “holes”, bipolar jets or other curious features and feeds the ISM with heavy chemical elements and energy.
One example for curious interstellar structures: The "Criss-Cross-Nebula (CCN)" and its "canopy" - a morphologically intricate gaseous nebula - was discovered by members of our institute in the nineties and was recently found to possess a very faint arc-shaped nebula. Interestingly, the CCN itself is a shock-excited nebula (excited by a nearby highly evolved supernova remnant), whereas the arc (called canopy), physically linked to the CCN, is photoionized. The source of the latter is hot inner gas of the supernova remnant, which has a leak towards the CCN.