  The magnetic nature of the formation of solar active regions lies at the
heart of understanding solar activity and, in particular, solar eruptions. A
widespread model, used in many theoretical studies, simulations and the
interpretation of observations is that the basic structure of an active region
is created by the emergence of a large tube of pre-twisted magnetic field.
Despite plausible reasons and the availability of various proxies suggesting
the veracity of this model, there has not yet been any direct observational
evidence of the emergence of large twisted magnetic flux tubes. Thus, the
fundamental question, "are active regions formed by large twisted flux tubes?"
has remained open. In this work, we answer this question in the affirmative and
provide direct evidence to support this. We do this by investigating a robust
topological quantity, called magnetic winding, in solar observations. This
quantity, combined with other signatures that are currently available, provides
the first direct evidence that large twisted flux tubes do emerge to create
active regions.
