Periods can be rough. Not only can be they be a pain to the max, but depending on where you are in your cycle your body could be experiencing any number of things. Some menstruation symptoms are more visible than others. According to Your Period, there are over 100 documented PMS symptoms, but what exactly is happening inside your body throughout the menstruation cycle?

There are four phases your body goes through from the moment the cycle begins to the moment it ends. Per Healthline, the phases are the menstrual phase, the follicular phase, the ovulation phase, and the luteal phase. All in all, the combination of all four phases can last anywhere between 24 to 38 days per Clue. What exactly happens during each phase? Find out below.

Menstrual phase

Every uterus wielder has an intimate knowledge of this phase. According to Mind Body Green, this is the first phase of the entire menstrual cycle and starts the first day you see a drop of red (or a crime scene, if you don’t catch it on time) in your undies. At this point, your progesterone — Healthline details that this is the hormone that gets your uterus ready for pregnancy and helps regulate your cycle — drops.

You may also find that you’re sleepier during this time, according to Mind Body Green. Clue explains that during this time, the unused egg and all the old gunk tissue is being shed (aka the endometrium or lining). An average period can last about five to eight days and the last day of bleeding marks the end of this luxurious phase.

Follicular phase

Now onto the ovaries and the follicle stimulating hormone — yay! Okay, so this next phase finds the uterine system sending a quick text to your pituitary gland (located in your brain) telling it that that you’re ready to prep another egg for ovulation. Healthline reports that this phase and the menstrual phase overlap, but unlike your period, this ends when you ovulate, marking another phase. This process is where the eggs come in and anywhere between five to 20 immature eggs can be involved.

Will all these eggs mature? Negative. Healthline notes that this is one of those “survival of the fittest” situations and only one will mature and release (unless your body is gunning for twins). So, what happens with the ones that didn’t mature? The body absorbs them and the mature one is sent off to a brand-spanking new cushiony bed made of endometrium lining to either be fertilized or die (marking the start of another bleeding phase). Clue notes that this phase typically lasts between 10 to 22 days depending on the uterine system.

Ovulation phase

So, the moment the egg is released the body automatically goes into the ovulation phase. Clue explains that this phase cuts the entire process in half (this is where the menstruation and follicular phases overlap). The ovulation phase is essentially everything your body has been prepping for — the big leagues, so to speak. Mind Body Green explains that once the egg makes it to where it needs to go, it will survive for about 12 to 24 hours. During this time, you’re also going to feel your most confident and most beautiful as both your estrogen and testosterone are at peak levels. So honey, go out there and peacock your life away.

Luteal phase

At this point in your cycle, everything begins to decline. Your estrogen, your testosterone, your confidence — all of it drops. Mind Body Green cites that this is when your body begins to feel those pesky PMS symptoms like bloating, breast tenderness, moodiness, the need to annihilate your enemies, and food cravings. At this time, progesterone production ramps up. Not only does this hormone help regulate the cycle, but it’s an anti-anxiety hormone as well.

But what happens if you happen to get pregnant during this phase? Healthline says the body starts the production of human chorionic gonadotropin. This is the hormone that pregnancy tests detect in the pee. If you’re not pregnant, the body reabsorbs the HCG and your cycle begins all over again. Per Clue, this phase can typically last anywhere between nine to 16 days (with 14 days been the average).