Ever watch a baby lying on his or her back take their toes and put them in their mouth. Now that's flexibility!!
That's how we all start but as the years pile up we begin to lose that ability to be so flexible. My experience is if one continues to do some form of stretching every day that flexibility diminishes at a much slower pace.
Simple stretching exercises can be done anywhere or anytime; when taking a brisk walk stop for a moment and touch your toes, when finishing a bike ride do a simple squat to help loosen your lower back, when waiting in a line reach for the sky with both arms up pulling upwards and you will feel the tension flow from your body. There are so many easy ways to stretch. So remember:
Keep it Simple, Consistent and Fun.