Phytoremediation is a process that uses plants (either directly or indirectly) to clean up contaminated soil or water; it has evolved into a more cost-effective, non-invasive, and socially acceptable approach for dealing with the cleanup of environmental contaminants. Plants can be used to absorb inorganic and organic pollutants, metabolically degrade organic pollutants, and encourage microbial degradation of organic pollutants in their root zones. A limitation to the widespread application of phytoremediation may be the limited habitat range or size of plants that have remediation potential, as well as the lack of tolerance by native plants to withstand detoxification and accumulation of contaminants. Understanding more about how pollutants might be removed from the root zone, along with a better understanding of plant–microbe interactions and their role in contaminant relationships, will help expand phytoremediation to more contaminated sites. Understanding the processes affecting pollutant availability (such as rhizosphere processes), pollutant uptake, translocation, chelation, degradation, and volatilization is needed. Plants can tolerate high pollutant loads; they can sometimes metabolize these chemicals into less toxic forms, and plants are known for their ability to catalyze the decomposition of organic materials in the rhizosphere. To date, it has not been conclusively demonstrated at many sites, nor is its effectiveness at full scale certain. Several aids have to be applied to address phytoremediation limitations: natural and chemical amendments, genetic engineering, and natural microbial stimulation.