Cilantro Root

The stems and leaves of cilantro are less heat resistant to cooking than the root. If using, it's best in the end as a garnish.

It is unboundedly worth the effort and the trial! The root has a slightly sweeter yet deeper taste and as PrettyPeas said, a noticable difference when grilled (or cooked for that matter) Many people think that cilantro tastes like soap, I happen to love the taste. The roots don't seem to have that same 'soapy' taste. Like Kitchen Butterfly, I freeze the root and use them later - they seem to do well that way. Try it! You will love them! I found a good photo...

http://www.google.fr/imgres?imgurl=http://www.blazinghotwok.com/uploaded_images/cilantroroots-709712.jpg&imgrefurl=http://www.blazinghotwok.com/2008/07/secret-ingredient.html&h=425&w=640&sz=64&tbnid=3vovnI4iopvc3M:&tbnh=91&tbnw=137&prev=/search%3Fq%3Dcilantro%2Broots%26tbm%3Disch%26tbo%3Du&zoom=1&q=cilantro+roots&usg=__jeMMiAK5TcffaDjWENXSnJGT2F0=&sa=X&ei=niDDTZGpK-_RiALasNSHAw&ved=0CEwQ9QEwCQ

I also use cilantro roots in Thai food, and I think it's better than the stems. It's one of my culinary pet peeves that so many markets remove the roots. And whenever I plant it, it just bolts.

I use cilantro roots in my green curries but when I can't find them, I sub the stems with no great loss of flavour. I often freeze my roots as I can never use them up before they go bad!

I use it anytime I can get my hands on it in Thai cooking. It's quite easy to chop, the difficult part is finding it. Even the cilantro I've grown myself tends to have spindly roots. The difference between roots and stems is noticeable in grilled chicken, though stems are fine. http://www.shesimmers.com/2011/04/thai-garlic-peppercorn-cilantro-root.html
Whenever I find cilantro with the roots still attached I buy more than I need and store the extra roots submerged in water in the fridge, changing the water every couple of days. They last longer this way.