Pulse Width Modulation (PWM) is a technique in which the width of a pulse is modulated keeping the time period of the wave constant. One cycle has a fixed time period called ‘Period’ and a varying on time called ‘Duty cycle’. The entire wave can have two voltages levels either logic 0 or logic 1. The PWM wave is very useful in the digital systems, since this can be used to generate different voltage values other than the logic 0 or logic 1 values. This feature is making use in so many digital systems like DC motor control, audio devices, simple decoration light controls etc.The PIC18F4550 has an inbuilt PWM module which can generate continuous PWM waves. The Period and the duty cycle of the PWMwave can be adjusted in program. This project explores the PWM module of the PIC18F4550 and tries to glow an LED with varying intensities, which shows that it is possible to generate any required voltage at a pin of a digital microcontroller with the help of PWM waves.