  We present an overview of the EAGLE science case, which spans
spatially-resolved spectroscopy of targets from five key science areas -
ranging from studies of heavily-obscured Galactic star clusters, right out to
the first galaxies at the highest redshifts. Here we summarise the requirements
adopted for study and also evaluate the availability of natural guide stars in
example fields, which will impact on the adaptive optics performance and
architecture.
