Phytolith studies are placed in the interaction of many scientific fields in both natural and human sciences. Although phytolith studies go back over 150 years, in the last 20 years they have increased substantially, with many publications in scientific journals of recognised quality. This book presents a review and synthesis of recent works in some areas of the Southeast and Southern Brazil and the Pampean Plain in Argentina, which have concentrated on numerous phytolith studies and may provide new contributions to the knowledge of phytoliths in these regions. This book has eleven chapters structured in sections. As an introduction a review of phytolith production and functions, organ and tissue localisation and distribution among plant families is presented. It also describes the main phytolith morphologies found in plants, soils and sediments and their taxon assignment. The taxonomic value of these amorphous silica biomineralisations and the classifications employed in different phytolith studies are also discussed. A summary of some phytolith indexes, used in palaeoenvironmental studies from different regions and based on the relative abundances of morphologies, is presented. Lastly, applications and limitations of phytolith studies are also mentioned.