Patches of tiny tracts of eggs on grass blades

Newbie here and asking for help please?
Please see attached photos.
We have just spotted 2-3 patches of tiny dense cream coloured eggs on the grass blades. Patches are about 30x40cm in 3 different areas. Lawn is otherwise healthy. Any idea what they are please and what to do about them?

 

It looks like one of the slime moulds that's fruiting.
It'll disappear completely in a few days and is harmless.
If you can get close with a magnifying glass, some of them are very beautiful.

 

Wow thanks Pete that’s most helpful and very interesting!

 

Very pretty!