I was really excited about finally getting to see the Sistine Chapel. And everyone also wants to see it because the crowd beelines for the sign that says Sistine Chapel but first you have to go through a million corridors before reaching it. You have to stand in a lot of lines and go through smaller corridors and stairs before finally reaching the chapel.
It's small! Very very small and you will be packed in like a cattle once you are inside. People do not move out. They do not make room. And you are stuck between humans and no air flow. It's hot and everyone is talking while being loudly hushed by Vatican guards. No photos are allowed inside the sacred chapel but people do it anyways. You will get in trouble with the guards if you get caught. Do not use your flash no matter what!
I stood inside the chapel no more than 5 minutes. I couldn't move or even tilt my head enough to see Michelangelo's beautiful ceiling frescoes. You will need a lot of patience to crane your neck without causing a neck injury. And be prepared to sweat it out and smell other people's body odor. There is no such thing as personal space here.
Overall, I suggest skipping the Sistine Chapel or lower your expectations a lot. Enjoy the museum instead and take your time going through it before proceeding to the chapel. I didn't get a chance to go inside the Basilica this time but that's for another trip to Rome!