Eta Carinae is one of the most extraordinary stars known in our galaxy, having many
peculiar properties. One of the most prominent features is that it is surrounded by
bipolar lobes called the Homunculus nebula. This nebula originated from the Great
Eruption in 1844 that was visible to the naked eye. It is also known that Eta Car had
other small eruptions centuries before the Great Eruption, where smaller ejectiles were
emitted with ~300 year intervals. Eta Car itself has extremely strong winds reaching
mass-loss rates of Mdot~10^{-3}Msun/yr, which interacts with the wind from a companion
star that orbits in a 5.5 yr period. Many attempts have been made to understand the
formation of Eta Car and its many peculiar properties, but most models have failed to
explain all features self-consistently. Here we propose a new scenario starting with a
hierarchical triple system. The system becomes unstable after mass-transfer in the inner
binary and reaches large eccentricities. Each periastron interaction peels off material
off the primary star and ejects them as outer ejecta. Then the instability eventually
triggers a merger, leading to the Great Eruption and formation of a bipolar nebula. In
this talk I will show results of 2.5D hydrodynamical simulations of a stellar merger and
show that it can reproduce the observed Homunculus nebula well. I will also discuss how
close periastron encounters in triple systems can reproduce the Outer ejecta via n-body
simulations. Understanding the formation of Eta Carinae helps us understand the
formation and evolution of LBVs in general, and possibly many other peculiar objects.