A natural pattern of sleep in a healthy adult should cycle between light and deep sleep phases as the human body naturally falls in and out of REM sleep. REM cycles typically last about 90 minutes each in contrast to periods of NREM (non REM) sleep which typically last about an hour. When viewing your sleep data graphs, an ideal night of sleep should alternate between light sleep(green) and deep/REM sleep(blue).
For more information about the various phases of sleep, check out the following link:
http://healthysleep.med.harvard.edu/healthy/science/what/sleep-patterns-rem-nrem