Bodyweight squats

Set your feet shoulder-width apart, toes slightly turned out. Pull in your lower abs, and keep your eyes forward.Slowly bend at the knees and drop your hips to lower your body. Keep your heels flat on the floor.  At the bottom of the exercise pause for a moment and strongly push back up to the starting position, mirroring the descent.Repeat for desired number of reps. 
Notes:
 Keep your back as straight as possible throughout the lift to avoid strain or injury.