  Observations of stellar kinematics, gas dynamics and masers around galactic
nuclei have now firmly established that many galaxies host central supermassive
black holes (SMBHs) with masses in the range $10^6 \sim 10^9$M$_{\odot}$.
However, how these SMBHs formed is not well understood. One reason for this
situation is the lack of observations of intermediate-mass BHs (IMBHs), which
could bridge the gap between stellar-mass BHs and SMBHs. Recently, this missing
link (i.e., an IMBH) has been found in observations made by the ASCA and the
Chandra of the central region of the starburst galaxy M82 \citep{MT99, PG99,
MT01, Ka01}. Subsequent observations by SUBARU have revealed that this IMBH
apparently coincides with a young compact star cluster. Based on these
findings, we suggest a new formation scenario for SMBHs. In this scenario,
IMBHs first form in young compact star clusters through runaway merging of
massive stars. While these IMBHs are forming, the host star clusters sink
toward the galactic nucleus through dynamical friction, and upon evaporation
deposit their IMBHs near the galactic center. The IMBHs then form binaries and
eventually merge via gravitational radiation, forming an SMBH.
