Jean, it was nerve racking for me also the first time as I was worried about scratching the "sensor". But the sensor has a layer of optical "glass" over it (AA/Low pass filter). Think of it as the front element of one of you lenses. It's glass but just use caution not to apply to much force with the cleaning tools. It will take a few tries to get it clean, my first wet cleaning left streaks on the optical glass. Just take your time and do it again until it's clean enough. Don't worry if there are a couple of small spots left after a few tries. They may fall off after some use of the camera. Just clean when you start noticing spots in images. Also look for some wet cleaning videos online as there are many from what people say.