In article ,
Melanie writes
I've just bought a tomato plant and an aubergine plant (the last ones in the
garden centre) but it's just occurred to me that I only have one plant of
each. Do I need at least 2 plants of each for cross-pollination, or will
they do their own thing by themselves?

You don't need two plants - they will mostly pollinate themselves.
Sometimes they can do with a little help with the first flowers, after
that they will continue self-pollinating through the season. You can use
either your fingers if you have a delicate touch, or (as I do) use a
very fine painting brush, like one from a kiddies painting set. Transfer
a little pollen from one open flower to another.

The same applies to peppers, chillies, cucumbers, melons, courgettes
etc. when grown indoors away from pollinating insects.
--
Alan & Joan Gould - North Lincs.