A brain–computer interface (BCI) establishes a direct communication channel between a brain and an external device. With recent advances in neurotechnology and artificial intelligence (AI), the brain signals in BCI communication have been advanced from sensation and perception to higher-level cognition activities. While the field of BCI has grown rapidly in the past decades, the core technologies and innovative ideas behind seemingly unrelated BCI systems have never been summarized from an evolutionary point of view. Here, we review various BCI paradigms and present an evolutionary model of generalized BCI technology which comprises three stages: interface, interaction, and intelligence (I3). We also highlight challenges, opportunities, and future perspectives in the development of new BCI technology. Classical brain–computer interface (BCI) systems are moving beyond lab demonstrations to real world applications with the development of associated hardware and software.Brain–computer interaction systems open up a wide range of BCI applications, especially in neural rehabilitation and human cognitive augmentation.Brain–computer intelligence systems reveal promising technologies for a new generation of artificial intelligence (AI) as well as a new generation of BCIs.