  Solar filaments, also called solar prominences when appearing above the solar
limb, are cold, dense materials suspended in the hot tenuous solar corona,
consisting of numerous long, fibril-like threads. These threads are the key to
disclosing the physics of solar filaments. Similar structures also exist in
galaxy clusters. Besides their mysterious formation, filament threads are
observed to move with alternating directions, which are called counterstreaming
flows. However, the origin of these flows has not been clarified yet. Here we
report that turbulent heating at the solar surface is the key, which randomly
evaporates materials from the solar surface to the corona, naturally
reproducing the formation and counterstreamings of the sparse threads in the
solar corona. We further suggest that while the cold H$\alpha$
counterstreamings are mainly due to longitudinal oscillations of the filament
threads, there are million-kelvin counterstreamings in the corona between
threads, which are alternating unidirectional flows.
