Whilst re-potting a miniature rose, I found a hell of a lot of these:

3mm in diameter.
Yellow.
Hard (brittle) thin shell.
Perfectly spherical.
One half was sometimes semi-translucent.
Filled with a white, milky fluid and a single black "spot".
"Pop" quite loudly when burst.

What are they?

Trouble?

-
[H]omer
(Gardening noob)