I found a cluster of bright green eggs on the underside of a leaf on my tomato plant. I live in Cambridgeshire in the UK. I took them into school to show the children I teach and they have hatched. They look like very small black/brown beetles? ( approx 1.5mm) They do not move and are all clustered together. I have never seen anything like them and I cannot find anything on the internet. What can they be?

Do you have a photograph?

Were the eggs in a line or a round cluster? They may be moth larvae rather than beetles. Have you looked at them under a lens? A picture would help.

I will try to photograph them tomorrow. Thanks

They were lined up in a four rows to make a cluster.
They were very bright green and about 1-2mm long.
They seemed to appear in the day... but I can't be sure of this fact.
The hatchings all look very small beetle like... not disimilar to a very, very tiny black ladybird but they are not moving and don't respond when touched?

I'm still thinking moth, but I'll wait on pix

Did they look like this?
Eggs and hatchlings - BugGuide.Net

Here are pictures of the various species of nymphs
pentatomid nymphs - Google Image Search