Since Thayer’s expedition in Brazil in 1865, scientists and explorers never stopped investigating the fish diversity of the Amazon Basin. In the 19th century, around 500 fish species were identified. After 1920, scientific missions have multiplied, exploring the major tributaries of the Amazon River in Bolivia, Peru, Colombia and Ecuador. In 1980, almost 1 500 species were known for Science. During the last decades, sampling effort considerably improved and the number of identified fish species increased, exceeding 2,400 species in 2020. Scientists are constantly discovering new species. The biodiversity inventory for the Amazon Basin is far from over!