Considering the process of bubble nucleation in AdS5, I will show how an effective 4D Friedman Robertson Walker cosmology emerges at the boundary of such bubbles. In this context the de Sitter temperature is interpreted as the Unruh temperature experienced by 5D accelerated observers on the bubble. I will then provide a 5D "holographic" construction of 4D matter, radiation and compact objects mimicking 4D black holes. The seminar will be based on 1807.01570 and 1907.04268.