Aligned non-spherical dust particles both polarize starlight passing through the dust cloud and emit polarized far infrared and sub-mm radiation. This provides an easy way to study magnetic fields in diffuse interstellar gas, hotbeds of star formation, circumstellar regions and interplanetary medium. The interpretation of the polarization in terms of magnetic field, however, requires the knowledge of the grain alignment history. This has been the stumbling block for reliable magnetic field tracing since the 50s of the previous century. While great minds, e.g. Ed Purcell and Lyman Spitzer worked productively in the field and contributed to it substantially, I shall show that the textbook solutions of the problem of grain alignment are not tenable for most of the interstellar grains. Instead, I shall identify grain helicity, which stems from their irregularity, as a most important component of a successful grain alignment theory. I shall demonstrate a simple analytical model of a helical grain that is able to explain the existing observational data (including the cases when the alignment fails) and thus allow more reliable studies of magnetic fields. I shall discuss a few new condensed matter effects, e.g. magneto-mechanical effects, which have been discovered in the process of the grain alignment research.