It is now established that interactions of elementary particles under the basic forces of nature are governed by what is known as the principle of gauge symmetry. Many aspects of this idea are tested experimentally to high level of satisfaction. At the same time, non-zero masses of elementary particles like the electron demands that the dynamics of their interactions are not perfectly symmetric under the gauge transformation prescribed by the otherwise successful Standard Model of Particle Physics. To understand the difficult task of breaking the electroweak symmetry (gauge symmetry corresponding to the lectromagnetic and weak-nuclear interactions) without spoiling the beauty of the gauge symmetry principle is the biggest challenges of today’s particle physics. The Large Hadron Collider, world’s biggest experimental facility, is specifically designed to address the electroweak symmetry breaking mechanism. The proposed experimental facility, the International Linear Collider (ILC), will also address various details of this mechanism. In this talk we will discuss some issues related to the electroweak symmetry breaking. To illustrate the related phenomenology, we will discuss one of our recent work on W-pair production at the ILC in the context of what is called the Littlest Higgs Model.