On: Inside the proton, the ‘most complicated thing you could possibly imagine’

[JumpCrisscross]

> neutrons described as a union of a proton and an electron based on masses

If you squish an electron and proton really hard, you'll get a neutron [1].

[1] https://en.wikipedia.org/wiki/Electron_degeneracy_pressure

[bigbillheck → JumpCrisscross]

And a neutrino: https://en.wikipedia.org/wiki/Electron_capture

[JumpCrisscross → bigbillheck]

If I understand correctly, which I probably don't, this is what releases the final wave of neutrinos in a supernova.