Ewww!! What are these?

[Flusie]

I was about to finally plant up a fern that’s been loitering in a pot in my garden for ages when I noticed some gatecrashers have moved in to the underside of virtually all of the leaves- it looks like they might be eggs of some description? Does anyone know what they are and should I be concerned? TIA!

I think they're baby fern spores.
www.gardeningknowhow.com/houseplants/ferns-houseplants/propagating-ferns.htm

Ferns are amazing!

Fern spores, that’s how they reproduce. Unless they are moving!

Oh my goodness, that’s amazing! I was worried I had a horrendous infestation of some kind! Thank you so much for your quick replies!