How to create a Custom Control in Silverlight?

I am working on Silverlight since 3 years and during the initial period I had a fear on creating Custom control. I was more confident creating UserControls during first one and half year of my job. But when I started working on custom controls, I came to know the power of custom control and all the fear gone out of my eyes.  It's around 2 years, I am working on it and every time I am exploring