Japanese people like to consume soy beans in many forms. The most well known soy bean product outside of the country is tofu, and edamame (green soy beans) is gaining in popularity too. There is one Japanese soy bean product that probably will never become very popular in other countries though, and that's natto.
Natto is probably the quintessential "weird food" of Japanese cuisine, like haggis in Scotland or lutefisk  in Norway. As a matter of fact, not even all Japanese people can tolerate it. People who live in the "western" (actually the south-western) half of Japan, who did not grow up eating natto, often despise it. But for those of us who grew up in the "eastern" half, natto is a really good thing.
What is natto then? It's steamed soy beans that have been fermented for a few days, with the addition of some beneficial bacteria (natto bacillus) that grow on rice straw. The soy beans are brown, soft and covered with sticky gooey matter, rather like the sticky slippery stuff that's inside an okra. If you saw this sort of sticky gooey stuff on food other than natto, you'd dump it immediately. But for some reason it's not going to kill you when it's on natto. As a matter of fact, natto is lauded as a health food, because the soy beans become very easy to digest when they've been natto-i-fied.
The other disturbing (for the uninitiated) aspect of natto is the smell. It can smell pretty strong, sort of like stinky socks. Some people can't stand this smell, and there are natto manufacturers now who produce an "odorless" or "low-odor" natto. I think that the smell is all part of the whole experience though.
This evening, as I mixed up a pack of natto for dinner, Max slowly backed away from with a look of sheer horror on his face. He can't stand the smell, he says. And believe me, Max is not a picky eater. He loves just about every other strange and exotic (to him) Japanese, Chinese, or any other type of food. He even loves those boiled chicken feet that is served at some dimsum places, though I can't even bear to look at them. But natto totally throws him off.
I do love natto though. The best way to have it is with a little soy sauce, a bit of hot mustard (most natto brands come with a tiny mustard pack), mixed well until plenty of gooey strings form around the beans. You can add a bit of chopped green onion if you like, or shredded nori seaweed. For extra sliminess, add a raw egg. This is great served on hot rice, or mixed with spaghettini. Unless of course, natto strikes horror in your heart too.
There is an excellent site about natto , if you want to see how gooey and stringy it can get. (Mine was not that gooey, probably because I had stored it in the freezer.)