Can you explain the lifecycle of an onion?

Looking for some #kitchentips! I've just learned that onions don't last forever (I knew that, but this is still surprising). I was away from home for ~10 days, so my onions weren't given the usual love they receive. Upon opening one to use tonight, with similar antennae as the uncut onion pictured here, I see that the middle is certainly less appealing and I won't be using it. Fear not, though! Casa de Aguilar lives the #nofoodwaste mantra, so I scooped out the less-appealing (by texture, that is. I'm all for #uglyproduce) and will use the healthy looking remnants. Can anyone explain what's going on in my most featured / rarely left out ingredient? #FoodRevolution