  We summarize the different puzzles raised by aging experiments of
spin-glasses and their various interpretations. We try to reconcile the `real
space', droplet like pictures with the hierarchical pictures that have been
proposed in the past. The basic ingredient is a strong separation of the time
scales that govern the dynamics of the system on different length scales.
Changing the temperature changes the length scale at which the system is
observed, thereby allowing rejuvenation (that concerns short length scales) and
memory (stored in long length scales) to coexist. We show that previous
experiments can be reanalyzed in terms of {\it vanishing energy barriers} at
the spin-glass transition, an important ingredient to obtain a fast separation
of time scales. We propose to distinguish between `fixed landscape
rejuvenation', which is already present in simple two (or multi) level systems,
from the `strong' chaos effect on scales larger than an `overlap length'
conjectured in the context of the droplet model. We argue that most experiments
can be accounted for without invoking the existence of an overlap length. New
experiments are presented to test some recent predictions of the strong chaos
scenario, with negative results.
