This book offers a quick and easy way to learn low-level programming of ARM microcontrollers using Assembly Language. The material of the book aims at those who has some experience in programming and wants to learn how to get more control over microcontroller hardware and software.Low-level programming comes into the category of more advanced programming and involves some knowledge of a target microcontroller. The material of this book is based upon the popular STM32 Cortex-M4 microcontrollers. It would be nice to have the datasheet, Programming and Reference Manuals on the particular STM32 microcontroller on hand while reading this book.All examples are developed using the NUCLEO-L476RG development board equipped with the STM32L476RGT6 Cortex microcontroller. The program code is developed using a free STM32CubeIDE version 1.4.2.The programming techniques described in this guide can also be applied to other development boards equipped with Cortex-M4/M7/L4 microcontrollers (STM32F4xx, STM32F7, etc.) with corresponding changes in source code. To develop the low-level code, the Assembler Language of STM32CubeIDE was used. This assembly language supports a subset of the ARM Thumb-2 instruction set that is a mix of 16- and 32-bit instructions designed to be very efficient when using together with high-level languages.