The Dutch site thinks it's better to wait with liver until they are 2 or 3 years old (or even older). The idea is that the liver is a detoxifying organ, which means that some of the toxins (such as heavy metals and PCBs) get stuck in the liver. This same detoxifying process does not work well yet in babies, so when they eat liver they might get some toxins they are not yet equipped to handle. I'm not sure I would wait that long with giving them liver myself (the husband does a very nice chicken liver "risotto"), but it might be good to be careful not to overdo it. And apropopos 'bubbles': aaaaawwww ....