We can't live without it, of course. Making up 21% of the air we breathe, oxygen is also the "O" in H2O meaning that it's probably the single most important element necessary for life. And yet in pure form oxygen is extremely toxic. It would thoroughly ravage a fine pair of lungs within a couple of breaths and the very air around you would ignite if you so much as thought of fire. Out of all the elements this one atom also indiscriminately pairs itself with just about every other to produce, of course, oxidation - sometimes a good thing, often not. Trapped as it is in here though, this little amount of 99.9% pure oxygen is completely harmless and you can safely mock it or admire it. Up to you!