Even though the metal-halide perovskites have been attracting ever-increasing interest for their breakthrough efficiencies in photovoltaics, light emitting diodes (LED), X-ray imaging, and general optoelectronics, it is not until very recently that metal-free halide perovskites became recognized as novel materials, not only for their good optoelectronic performance, but also for their wide chemical  diversity, tunability, light weight, mechanical flexibility and eco-friendly processability. The community is turning attention to these lightweight semiconductors and promising results have been achieved in the initial evaluation of crystal structure and a range of properties including ferroelectric and optoelectronic properties. In this comment, the crystal structure and synthesis of these materials are discussed together with the various properties that have been studied for these materials. Future prospects are further discussed for chemical diversity, structure tunability, synthetic process, potential properties, optoelectronic and energy-related applications.