Sleep of the typical person usually consists of sleep cycles, each of which lasts about 90 minutes.
The first stage of this cycle is light sleep and it lasts for about 45 minutes.
The second stage is deep sleep, which is very important for rest of Your brain. You do not normally have dreams at this sleep state, it is hard to wake You up while deep sleep. It also usually lasts for about 45 minutes.
The third and last state in the sleep cycle is called rapid eye movement (REM). On the contrary to the previous stage, during the REM stage Your brain is even more active than when You are awake, You process new information, analyze some important situations, dream. Your eyes are active and follow the actions of Your dream (which is the grounds of the calling of this stage). The REM stage lasts for 20-30 minutes.
The full sleep cycle normally repeats about 4 times each night.
Measuring sleep stages with Mi Band 1s is benefiсial for getting up feeling calm and rested with Mi Heart Rate app:
You may monitor Your sleep stages with Mi Band 1s and MiBand 2. More info on which band is better for this can be found there: