1933年10月,巴黎世界度量衡大会采纳米的新的定义,根据美国国家标准计量委员会的“标准计量报告”,这是23年来,国际单位制7个基本单位中的第一个变动单位。米定义的变化不会影响米的实际长度,作一般测量也不会有明显的影响,然而,在一些技术领域的精密测量上有着重要意义, In October 1933, the new definition of nanotechnology adopted by the Paris Metrometric Conference was based on the “Standard Measurement Report” of the National Standards Measurement Committee of the United States. This is the first change unit of the seven basic units of the International System of Units for 23 years. Changes in the definition of rice do not affect the actual length of the rice, nor do they have a significant impact on general measurements. However, there are important implications in the precision measurement of some technical fields.