A time traveler's survival guide. The vertical green bars are the only times in Earth's history with enough oxygen to breathe (hypoxia) and low enough to avoid oxygen toxicity (hyperoxia).
This was a screenshot I took months ago while watching a Geology Hub upload on YT. It was a lightbulb moment for my understanding of mass extinction events, (the largest was 250ma). I've referenced this multiple times, so thought I might share. Perhaps you find it as interesting as I do.