Scientists use a variety of technologies to collect samples in the Arctic. Some scientists collect ice cores, which provides insight on past climate and ecological conditions. Others are interested in the sediments on the seafloor and use tools such as box cores to retrieve samples of mud from the frigid waters. Plankton nets and trawls are great for sampling biodiversity in the Arctic waters. Plankton nets, which have tiny pores, are pulled behind the vessel to filter microscopic plankton out of the water column. Large trawls nets are used to sample the mid-water or benthic (seafloor) ecosystems. Both of these nets yield large samples that require many hands to sort and process for further study. Water samples are often collected to examine microbes and the chemical composition of the Arctic waters. Specialized underwater robots like the Nereid Under Ice also help scientists collect samples and visualize the underwater Arctic world.