Dust commonly found around the house has thousands of different microbes species, which are some of the smallest living beings known to exist.
According to BBC News, authors of a study published in the journal Proceedings of the Royal Society B analyzed dust from 1,200 homes in the United States. They found more than 9,000 different species of microbes, also known as microorganisms.
"Our homes are ecosystems," study co-author Noah Fierer, a microbial ecologist at the University of Colorado - Boulder, told Live Science. "We live with an amazing diversity of microorganisms that we usually do not see.
"I then started thinking about how one environment we spend the majority of our time in is the home.
"What types of microbes are found in our homes, and how do they vary?"
The researchers chose to gather dust samples from the ledge above the home's front door, BBC News noted, because people often miss it when cleaning. In addition to all the different kinds of microbes, the researchers also found about 2,000 different types of fungi.
"Most of the fungi we are seeing in the home appears to be coming from outside the home," Fierer told BBC News. "They enter the home on our clothing, or through open windows or through doors.
"Therefore the best predictor of what types of fungi are in your home is where your home is located."
The researchers also found different species of fungi and microbes depending on where the home was and who was living in it.
"We found distinct bacteria in homes that had women and homes that were male-only," Fierer said. "There are some kinds of bacteria that are more common on women's bodies than on men's, and we can see the impact of that on the bacteria found in house dust.
"It was surprising to us that it was such a strong influence - stronger than any other factor, stronger than where your home was located or the design of your home, for example."
