Hair is straightened to improve manageability and provide style versatility. To straighten hair, an alteration of the cortex must occur. To achieve temporary straightening – a lower energy process – hydrogen bonds and salt linkages are altered while permanent straightening is achieved through the modification of covalent bonds, which requires more energy. Permanent hair straightening can be accomplished with ammonium thioglycolate, sulfites, and hydroxide. Hair straightening treatments are popular and can be used to achieve individually desired styles. However, care must be taken to decrease the chances of overprocessing that may occur when processes and chemical treatments are performed improperly. The future of straightening processes and treatments is only limited by science and technology. History shows that even though there have been major scientific advancements, the technology to straighten hair either temporarily or permanently still involves the use of heat with mechanical stress or chemical products. Over time, incremental improvements in thermal appliances and formulations for chemical treatments will continue to occur. Despite the advances, it will remain important to understand the advantages and disadvantages and proper techniques of each method based on personal style preference, hair type, and quality to reduce adverse effects.