OGLE-ing the Magellanic System: Three-Dimensional Structure of the
  Clouds and the Bridge Using Classical Cepheids
  We analyzed a sample of 9418 fundamental-mode and first-overtone Classical
Cepheids from the OGLE-IV Collection of Classical Cepheids. The distance to
each Cepheid was calculated using the period-luminosity relation for the
Wesenheit magnitude, fitted to our data.
  The classical Cepheids in the LMC are situated mainly in the bar and in the
northern arm. The eastern part of the LMC is closer to us and the plane fit to
the whole LMC sample yields the inclination $i=24.2\pm0.7$ deg and position
angle ${\rm P.A.}=151.4\pm1.7$ deg. We redefined the LMC bar by extending it in
the western direction and found no offset from the plane of the LMC contrary to
previous studies. On the other hand, we found that the northern arm is offset
from a plane by about $-0.5$ kpc, which was not observed before. The age
distribution of the LMC Cepheids shows one maximum at about 100 Myr.
  We demonstrate that the SMC has a non-planar structure and can be described
as an extended ellipsoid. We identified two large ellipsoidal off-axis
structures in the SMC. The northern one is located closer to us and is younger,
while the south-western is farther and older. The age distribution of the SMC
Cepheids is bimodal with one maximum at 110 Myr, and another one at 220 Myr.
Younger stars are located in the closer part of this galaxy while older ones
are more distant.
  We classified nine Cepheids from our sample as Magellanic Bridge objects.
These Cepheids show a large spread in three-dimensions although five of them
form a connection between the Clouds. The closest one is closer than any of the
LMC Cepheids, while the farthest one -- farther than any SMC Cepheid. All but
one Cepheids in the Magellanic Bridge are younger than 300 Myr. The oldest one
can be associated with the SMC Wing.
