Types of articles PLOS ONE welcomes original research submissions from the natural sciences, medical research, engineering, as well as the related social sciences and humanities, including: Primary research that contributes to the base of scientific knowledge, including interdisciplinary, replication studies, and negative or null results. Systematic reviews whose methods ensure the comprehensive and unbiased sampling of existing literature. Submissions describing methods, software, databases, or other tools that meet the journal’s criteria for utility, validation and availability. Qualitative research that adheres to appropriate study design and reporting guidelines.