Your Steel lets you track your sleep without requiring any action on your part. All you have to do is wear your Steel to sleep: it will do the rest on its own.
If you do not want to track your sleep, remove your Steel before going to sleep.
Retrieving your Sleep Data
You can retrieve the sleep data collected by your Steel in your Timeline or on your Measures tab in the Withings App™.
White: time spent out of bed - Grey: time spent awake (in bed) - Medium blue: duration of light sleep - Dark blue: duration of deep sleep
The Withings App keeps your entire history, allowing you to easily track how your sleep data evolves over time.