Nearly every substance is denser as a solid than as a liquid. Water is one of the rare exceptions: ice is about 8% less dense, and liquid water is densest at around 4 °C. In winter, that 4 °C water settles at the bottom of lakes while floating ice insulates the surface. Fish survive thanks to this oddity.
Cooled below −183 °C, oxygen turns into a pale blue liquid. Pour it between the poles of a strong magnet and, instead of flowing away, it hangs suspended between them. The reason lies in its unpaired electrons, which respond to the magnetic field. Liquid nitrogen, by contrast, is colourless and pours straight through.
In 2012, Felix Baumgartner jumped from a capsule hanging beneath a balloon, about 39 kilometres up. In that extremely thin air almost nothing slowed him down, and he reached around 1,358 km/h in free fall, or Mach 1.25. He became the first person to exceed the speed of sound with nothing but his own body.