  The lattice of the set partitions of $[n]$ ordered by refinement is studied.
Given a map $\phi: [n] \rightarrow [n]$, by taking preimages of elements we
construct a partition of $[n]$. Suppose $t$ partitions $p_1,p_2,\dots,p_t$ are
chosen independently according to the uniform measure on the set of mappings
$[n]\rightarrow [n]$. The probability that the coarsest refinement of all
$p_i$'s is the finest partitions $\{\{1\},\dots,\{n\}\}$ is shown to approach
$1$ for any $t\geq 3$ and $e^{-1/2}$ for $t=2$. The probability that the finest
coarsening of all $p_i$'s is the one-block partition is shown to approach 1 if
$t(n)-\log{n}\rightarrow \infty$ and $0$ if $t(n)-\log{n}\rightarrow -\infty$.
The size of the maximal block of the finest coarsening of all $p_i$'s for a
fixed $t$ is also studied.
