Most people have pulled long-forgotten vegetables from their refrigerator's depths at least once, and just the memory is enough to make a stomach turn. But one man's fridge mold is another man's still life. Estonian artist Heikki Leis' Afterlife is a veritable rotting cornucopia of vegetables photographed long past their prime. "I was inspired by some potatoes I had once left out in a pot for too long. They had started to mold and on closer examination the colors and textures looked interesting enough to take some photos," Leis wrote in an e-mail. Leis then started experimenting with various fruits and vegetables. He sometimes let them decay for two months, keeping them covered so they wouldn't dry out. When Leis finished, he was truly finished. "I'm tempted to say I ate them, but the truth is I just threw them away," he said. Leis said he'd be open to an expert's analysis of his rotting concoctions, so Wired invited mycologist Kathie Hodge of Cornell University, who's working on a book about food-decaying fungi, to look at the work. There are thousands of molds out there, and "we see them all the time and yet we don't look at them. They live with us and we automatically throw these things out," said Hodge, who took Wired on a tour of Leis' moldy world, though not without a warning. "Getting them to this level is probably not a good idea, so don't try this at home!" she said. Image: Swede mold. Heikki Leis. (A swede is a type of turnip).

Wired: How do we interact with fungi? Kathie Hodge: They have a huge impact on our lives. A third of food is lost to spoilage, and most of that is due either to mold or bacteria. Within the realm of the kitchen, some fungi are plant pathogens. For example, when you find a lemon with blue mold, that's a disease the lemon got in the field. That fungus has been eating it all along, despite how well you've washed it. But you don't notice it until it erupts in your kitchen. Others may colonize the remnants of your grilled cheese sandwich. In the kitchen there are some notorious ones, like penicillium. It's the same group of fungi that gives us penicillium, but the genus includes many different species. They're very good at living with people and very good at eating our stuff. There are good and evil fungi. Some are great friends of mankind. Image: Corn mold. Heikki Leis.

Wired: What chemical changes take place in food as it rots? Hodge: There are lots of different answers to that question. It depends on what fungi are eating them. Generally, when fungi grow on something, they secrete digestive juices. So the impact of fungi actually goes beyond the boundaries of their cells. They secrete things into their environment and absorb the products of digestion back into themselves. Some fungi will like to eat your sandwich. Some are good at eating your fruit. Different fungal species have different arsenals of enzymes that they use to digest their food. Some molds are very good at breaking down cellulose. Others are very good at breaking down protein. Molds look gross from a distance but close up they have a beautiful and highly organized structure. They're very efficient at what they do. Image: Pumpkin mold. Heikki Leis.

Wired: Leis mentioned that his rotting vegetables gave off a less-than-pleasant smell. Why do rotting foods smell so bad? Hodge: I think it doesn't smell so bad. It just smells. Over a long evolutionary time, humans probably evolved the perception that it's a bad smell. We've learned to avoid eating rotting food by perceiving it as bad. For flies it might be a good smell. If we feel disgust, we're unlikely to want to eat it. This probably helped our ancestors survive. Image: Potato mold. Heikki Leis.

Wired: Have you ever tasted rotting food? Hodge: I've never done that experiment. A lot of rotting food contains a fair number of penicillium fungi, which make toxins. You'd probably feel sick if you ate something as moldy as anything in one of these photographs. Frankly, it would be hard to eat if you had a sense of smell! Though there are also some foods that are purposely rotten with fungi, like blue cheese and tempeh. I love blue cheese. I had a nice fungus-fermented cheese in my lunch the other day. Image: Close-up of corn mold. Heikki Leis.

Wired: What kinds of molds are growing on the Afterlife vegetables? Hodge: The really interesting thing is many are household molds. It seems that the artist may have a penicillium issue in his studio. Most of the blue-grey molds are species of penicillium. If you blew on that, there would be a whirlwind containing hundreds of thousands of spores. For most of these, you need a microscope to really know. But that big hairy beard [on the potato above] is rhizopus stolonifer. It looks like a fuzzy dead animal. Rhizopus, which means root foot, is a common genus of mold. It's really good at growing on leftovers. On top [of the potato], it looks like trichoderma, but I can't be too sure. That's another [fungus] that likes to live with us. Sometimes it eats other fungi. Even within the mold community there are evil molds. Sometimes trichoderma is a pathogen. Often it's found in soils. That's why we may be seeing it on a potato. Image: Potato mold. Heikki Leis.

Wired: What about the swede, or rutabaga, mold? Hodge: That's a good one! There's a rhizopus beard around the bottom anchoring it to the ground. The blue postules may be penicillium, a really common spoilage fungus. There are probably eight to 10 different molds growing there. I've never worked on rutabagas, so I couldn't tell you for sure. Image: Swede mold. Heikki Leis.

Wired: Leis mentioned the beet root was his favorite. Can you tell us about its molds? Hodge: Isn't it beautiful? It's so hairy. There are fungi on the surface on the wrinkly beet skin, but I can't guess at what they might be. But it looks like the fungus digested parts of it and then absorbed it into its mycelium. The fluff is the fungus fruiting. Its function is to make more spores. Each hair ends in a sphere with spores that will then look for the next victim. Image: Beet mold. Heikki Leis.

Wired: What about in this other beet root photograph? Hodge: Those blue-green postules are most likely penecillium. It's done a very good job of eating that beet. The rhizopus beard has subsided. The droplets are just a liquid byproduct of decay. There's probably fungal metabolites that give it a bit of color. There's probably some mycotoxins in there, so I wouldn't put my tongue on that. Image: Beet mold. Heikki Leis.

Wired: You almost refer to molds and fungi as if they were people. Hodge: They're just beautiful and magical. They're moody and expressive. I'm fascinated by the small world at the threshold of human vision. I forget sometimes that being a person who likes molds is weird! But I won't give them up. They're so cool. Maybe it's like having obnoxious neighbors. Why expend energy shunning and avoiding them? You might as well befriend them. They probably have interesting parties. Image: Close up of beet mold. Heikki Leis.