One of the best exercises for legs and complex body development.
Stand up straight with your feet shoulder width apart.
As you inhale deeply, lower yourself slowly and bend your knees.
You can slightly bend your torso forward but keep your back totally straight. You should move your hip joints only.
When your thighs get parallel to the floor or slightly lower, exhale and straighten your knees and your torso.
Without straightening your knees completely, repeat the exercise.
While going up, the knees should remain parallel. During the squat, your knees should be pointed in the same direction as your feet.
Deep squat is natural movement for knee joint. Partial squats (½ or ¼ of the full range of movement) have a negative impact on the knee joints and lower back.