At 6 weeks the baby is called an embryo. On a sonogram at 6 weeks they look like a small blob or dot on the sonogram depending on the equipment used. Sometimes you can't see anything at all. The embryo will look more like a kidney bean around 8 weeks.
Just like a little kidney bean. It's not really much but it's always good to see something. They may even be able to hear the heartbeat.
You can try Googling and you can see a whole bunch of images.