In the research of sleep, every night, we are going through different stages of sleep. From a dreaming phase (REM), we go into light sleep, followed by deep sleep and then cycle back again. Between a light sleep and dreaming phase, there are these almost-awake moments, where we are closest to awakening.
This moment is called ‘Wachmoment’, the ideal moment in which a sleep phase alarm clock is supposed to wake you up and when you will wake up fresh and full of energy.