What is this seedling please?
 

I have it from a packet of mixed seeds - it had a black triangular flat seed about 4 or 5mm long. The first pair of leaves have 2 lobes each, but each leaf is "U" shaped, so that the pair of leaves together look rather like the shape of a gene/chromosome pair. The second pair of leaves look like they will be heart shaped but are only just starting to unfurl.

It looks like Morning Glory, a climber, usually has blue flowers. Only problem is its very tender.

Thanx Ganggang
I have checked up on the web, and am now very exited (I lead a sheltered life) about having these in my garden. Hubby not too chuffed I think, as they are similar to convulvulus in appearance, but they are annuals so will not take over, I hope??

Well, I looked after them like they were my own flesh and blood. And what did they do????....Died out of spite!!!
Well actualy, I ignored the fact that hey were called "Morning Glory" and didn't give them enough light. But better luck this year, thanks to folk here, I now know what tolook for.
G