Based on a total of 8,218 pelagic microplastic samples from the world's oceans collected between 2000 and 2019, a team of scientists has developed a publicly available dataset for assessing the abundance of microplastics and their long-term trend in the world's upper oceans. The team found 24.4 trillion pieces (82,000--578,000 tons) of microplastics in the world's oceans, but the actual amount is likely to be much greater.