It is known that many simply connected, smooth topological
4-manifolds admit infinitely many smooth structures. The smaller the Euler
characteristic, the harder it is to construct exotic smooth structure.

In this talk we present examples of symplectic 4-manifolds with same
integral cohomology as S^2 x S^2. We also discuss the generalization of
these examples to #(2n-1) S^2 x S^2 for n > 1. As an application of these
symplectic building blocks, we construct exotic smooth structure on small
4-manifolds such as CP^2#k(-CP^2) for k = 2, 3, 4, 5 and 3CP^2#l(-CP^2) for
l = 4, 5, 6, 7. We will also discuss an interesting applications to the
geography of minimal symplectic 4-manifolds.