Carbon is a unique and versatile element that is capable of forming different architectures at nanoscale. The element has become a key component in nanoscience and nanotechnology. Transmission electron microscopy (TEM) acts as "our eyes" enabling us not only to reveal the morphology, but also to provide structural, chemical and electronic information of nanocarbon on the atomic level. In fact, except for fullerene, nearly all types of carbon nanomaterials were discovered by TEM, such as carbon nanotubes, carbon nanocones, and graphene-like nanocarbon. It cannot be imagined what nanoscience and nanotechnology would be without the contributions of TEM. Herein, the "interaction" between TEM and the science of carbon nanomaterials is reviewed and it is demonstrated for some selected examples that TEM provides a dramatic driving force for the development of nanocarbon science. Advanced transmission electron microscopy techniques are powerful and versatile research tools for investigating the morphology, structural, chemical and electronic information of complex carbon nanomaterials. Such information has been established as a guiding light in synthesis of newly formed nanocarbon with novel performances and as a key to understanding the function. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.