I have a confession to make: Sleep is not as black and white as we think it is.
Another confession: What appear to be reasonable questions--with easy answers!--turn out to be far more complex than a simple "yes/no."
Even the basic question "why do we sleep" has no clear-cut answer. We here at Zeo are adult enough to admit that sleep science doesn't know everything, but we can explain why this is the case--as well as answer 3 questions every Zeo user asks.
In the beginning we slept--and that fact didn't bother us too much. There were a bunch of ideas as to why this happened but for the most part, they were stabs in the dark. 
Then we realized that we could explore the human body without cutting it open and got excited. When we started building monitoring systems and adding electricity to dive further into ourselves, we got super excited and really, haven't ever come down from that high since.
However-- The field that is sleep medicine (a.k.a. what Sleep Science is called by the PhDs) is still a new and tiny field. The use of EEG only started to be codified in the 1960s. The first US sleep clinics opened in the 1970s. It put in all in perspective, electric typewriters and graphing calculators were that day's MacBoook and iPhone. Heck, having 8 tracks of music all at once was a big deal.
Now into this world comes reams and reams of data from stuff you never knew existed--but happens every night in every single human being--and you have to make sense of it all. Needless to say, it's taken a good 30 years just to figure that early stuff out.
Admittedly, one of the best ways to deal with tons of information is to just explore. Kids do it all the time and we call it "play". Scientists call it "research" but it's a remarkably similar process that goes a little something like this:
You ask questions, you test things out, and compare results. Then you do it all over again.
Sound familiar?
This is what you do all the time with your Zeo. You use it, get data, ask questions ("Why did my deep sleep tank last night?"), then search for answers. You journal your experiments every day, and post the results for others to comment on. If you already do these basic things, you're already well on your way to being a sleep expert.
Of course, in every field there are some basic things that you just need to know to get started. To step up your Sleep IQ,here are answers to the three sleep questions every Zeo user asks.
The short answer is "No". The caviate is that we don't always know why.
Some of it is certainly related to lifestyle--not making sleep a high priority as part of our overall life is certainly a culprit--but some of it could be biology. Even things like the "90 minute sleep cycle" turns out to differ from person to person. Age and sex are turning out to be factors in one's overall sleep quality too.
Since we're still asking why this happens and what it means, it's important to focus on what sleep is to you, not your partner, parent, or friend.
Again, the short answer appears to be "No", but that's not the same as your sleep ratios not meaning something to you.
While we do know that our sleep ratios fluxuate from night to night--and that external factors can influence those ratios--whether or not an incease in REM means that Light sleep was "converted" into another stage is not known.
Given the fact that each stage does different things, it's perhaps better to think of them as internal organs; if your kidneys underperform, your stomach isn't going to "step in" and become a kidney for a day or two.
Cut back or completely cut out caffeine & alcohol from your diet. Get regular exercise. Don't go to bed stressed out. Quit smoking. Get 7-9 hours of sleep per night/every night and go to bed and wake up at the same time.
If this sounds familiar to what your doctor might say, keep in mind that an end goal of sleep is to keep you healthy.
Scientists have shown that all the above have measurable effects on your sleep quality and composition; namely, that this sh*t harms our sleep. You can experiment with supplements and OTC things but if you haven't toyed with these factors yet, you're missing out.
There's a great thread on the forum from chrismv48 that asks all these questions--as well as a few others--to the Zeo community at large. Now that you know a few more of the ins and outs of being a sleep scientist, why don't you join the discussion?
Share your data, look for larger trends, play and most of all, have fun.
Jump in to add your 2ยข and teach us a thing or two!