  We study the formation of singularities for the mean curvature flow of
monotone Lagrangians in $\C^n$. More precisely, we show that if singularities
happen before a critical time then the tangent flow can be decomposed into a
finite union of area-minimizing Lagrangian cones (Slag cones). When $n=2$, we
can improve this result by showing that connected components of the rescaled
flow converge to an area-minimizing cone, as opposed to possible non-area
minimizing union of Slag cones. In the last section, we give specific examples
for which such singularity formation occurs.
