In this book, we will delve into the latest advancements and discoveries in the field of hyaluronic acid filler injections. Hyaluronic acid filler injection stands out as one of the most frequently performed aesthetic procedures globally. The chapters within will encompass recent technological innovations related to hyaluronic acid fillers, encompassing key aspects such as rheology, cohesiveness, degree modification, NMR data, and information on impurities. Additionally, the book will feature up-to-date techniques for safe procedures employing Doppler ultrasound and explore potential treatments for ocular complications.