The eternal lab dilemma! On the left, we've got "in vivo" testing (Latin for "within the living") with our adorable little lab mouse friend who's probably thinking "I didn't sign up for this career path." On the right, "in vitro" testing (Latin for "in glass") with cells growing in a petri dish who never complain about the experimental conditions. These two approaches are basically the scientific equivalent of choosing between a complicated relationship and a Netflix subscription. In vivo gives you the full biological complexity but comes with ethical committees, animal care protocols, and tiny mouse-sized escape attempts. In vitro is cleaner, more controlled, and nobody calls PETA—but might not tell you how things work in an actual organism. Could science manage without them? That's like asking if a chemist could work without coffee—theoretically yes, practically NOPE!