As a foundation of digital transformation, digital twins are critical for achieving smart manufacturing. Recent technology advancements, such as smart sensors, Internet of Things (IoT), cloud computing, machine learning, and artificial intelligence (AI), have enabled digitalization in manufacturing and facilitated the development of digital twins in manufacturing. However, because of its interdisciplinary nature and complexity, guidance is still needed for the implementation of digital twins in manufacturing systems and to ensure that the digital twin developed is trustworthy. This paper discusses manufacturing digital twin use cases, benefits, common challenges for implementing digital twins, relevant standards organizations and industry consortia efforts, as well as ongoing efforts towards digital twin standards, focusing on the new ISO standard, ISO 23247 - Digital Twin Framework for Manufacturing, and discusses digital twin standards development procedures.