Or other smaller nuclei.

I'm not sure what 3 1/2 gallons of any nuclei look like but I'm pretty sure I would not want to be trying to put it into anything.

You'd definitely need a very good magnifying glass.

Feel that this should be raised with @xkcd.com. What exactly would 3.5 gallons of nuclei look like? What would be a safe distance to observe it from? (Before it's been threaded into our Hubble-barn shaped Hubble Barn)

Paging Dr Monroe 😁. My guess is that it would be a bit of a neutron star and so 3.5 gallons (UK or US) would be bloody heavy in total.