  This paper uses the caustic crossing events in the microlens data sets to
explore the nature and location of the lenses. We conclude that the large
majority of lenses, whether they are luminous or dark, are likely to be
binaries. Further, we demonstrate that blending is an important feature of all
the data sets. An additional interpretation suggested by the data, that the
caustic crossing events along the directions to the Magellanic Clouds are due
to lenses located in the Clouds, implies that most of the LMC/SMC events to
date are due to lenses in the Magellanic Clouds. All of these conclusions can
be tested. If they are correct, a large fraction of lenses along the direction
to the LMC may be ordinary stellar binary systems, just as are the majority of
the lenses along the direction to the Bulge. Thus, a better understanding of
the larger-than-anticipated value derived for the Bulge optical depth may allow
us to better interpret the large value derived for the optical depth to the
LMC. Indeed, binarity and blending in the data sets may illuminate connections
among several other puzzles: the dearth of binary-source light curves, the
dearth of non-caustic-crossing perturbed binary-lens events, and the dearth of
obviously blended point-lens events.
