Solar filaments are an intriguing phenomenon, like cool clouds suspended in the hot corona.Similar structures exist in the intergalactic medium as well. Despite being a long-studied topic, solar filaments have continually attracted intensive attention because of their link to coronal heating, coronal seismology, solar flares and coronal mass ejections (CMEs). In this review paper, by combing through the solar filament-related work done in the past decade, we discuss several controversial topics, such as the fine structures, dynamics, magnetic configurations and helicity of filaments. With high-resolution and high-sensitivity observations, combined with numerical simulations, it is expected that resolving these disputes will definitely lead to a huge leap in understanding the physics related to solar filaments, and even shed light on galactic filaments.