  We analyze non-Higgsable clusters of gauge groups and matter that can arise
at the level of geometry in 4D F-theory models. Non-Higgsable clusters seem to
be generic features of F-theory compactifications, and give rise naturally to
structures that include the nonabelian part of the standard model gauge group
and certain specific types of potential dark matter candidates. In particular,
there are nine distinct single nonabelian gauge group factors, and only five
distinct products of two nonabelian gauge group factors with matter, including
$SU(3) \times SU(2)$, that can be realized through 4D non-Higgsable clusters.
There are also more complicated configurations involving more than two gauge
factors; in particular, the collection of gauge group factors with jointly
charged matter can exhibit branchings, loops, and long linear chains.
