Title text:
With their 13 years recording and performing together and two humans worth of mass, the White Stripes are sandwiched neatly between gray wolves and blue whales.
Transcript:
Transcript will show once it’s been added to explainxkcd.com
Source: https://xkcd.com/3283/
Gravity must be able to hold it together for it to be a black hole. The limiting factor is Hawking radiation, which also applies to larger black holes, but the smaller they are, the faster they evaporate from that. To the point where it does explode if it's too small.