<s>[INST] What happened to the dinosaurs? [/INST] The dinosaurs went extinct around 65 million years ago. The exact cause of their extinction is still the subject of scientific debate, but the most widely accepted explanation is that a large asteroid impact caused massive fires, tsunamis, and a "nuclear winter" effect, which blocked out the sun and dramatically cooled the planet, killing off the dinosaurs and many other species.

Additionally, volcanic activity and sea level changes, as well as competition with newly evolved mammals, may have also contributed to the decline of the dinosaurs. However, the asteroid impact remains the most significant factor in their extinction.

It's worth noting that not all dinosaurs went extinct, as birds are direct descendants of a group of small, feathered dinosaurs. So, in a sense, dinosaurs still exist today, albeit in a much different form than the massive reptiles that once dominated the planet. </s>