A jet model represents well different X-ray states of the bright ULX IC342 X-1.

The Galactic center (GC), being the closest nucleus, holds a position of privilege in the study of galaxy centers, but because it is edge-on and hidden behind 30 magnitudes of visual extinction it is often difficult to understand the overall structure of the region. Nearby galactic nuclei potentially provide a guide to understanding the large-scale structure of the GC. High resolution maps of molecular line emission along with radio and optical continuum towards the nucleus of the nearby, face-on spiral IC 342 are discussed. Attention is focused on a comparison of the large-scale morphology, gas chemistry, and star formation between the two nuclei. The case is made that IC 342 is one of the best extragalactic templates for the GC. Both have a star formation rate within a factor of two of each other and an ISM morphology characterized by a R 300 pc central molecular zone formed from a pair of arms laced with a collection of dense star forming molecular clouds. IC 342 also exhibits a nuclear cluster and associated circumnuclear disk. Whether the nuclear morphology and chemistry in IC 342 is an extension of the disk bar, a separate nuclear bar, or results from radiative/mechanical feedback remains unsettled.

We present optical observations of an ultraluminous X-ray source (ULX) in Holmberg IX, a dwarf galaxy near M81. The ULX has an average X-ray luminosity of some $10^{40}$ erg/s. It is located in a huge (400pc$\,{\times}\,$300pc) ionized nebula being much larger than normal supernova remnants. From the observed emission lines (widths and ratios) we find that the structure is due to collisional excitation by shocks, rather than by photoionization.

We identify the optical counterpart to be a 22.8 mag blue star ($M_V=-5.0$) belonging to a small stellar cluster. From isochrone fitting of our multi-colour photometry we determine a cluster age of some 60 Myr. We also discovered strong stellar HeII$\lambda$4686 emission (equivalent width of $\mbox{10 \AA}$) which proves the identification with the X-ray source, and which suggests the presence of an X-ray heated accretion disc around the putative black hole.