For functional materials that are in a nascent stage, such as the antiferromagnetic spintronics, quantum information storage, and new semiconducting compounds, it is not clear what will be the high-performance materials of tomorrow. There is a pressing need to examine the complex properties of these emerging materials, and growing single crystals is a crucial step toward investigating their properties in detail. I will explain why measuring transport, optical, and magnetic properties are important in these systems, and how to determine their anisotropy. Due to the required millimeter dimensions, they must be grown from solutions, fluxes, or vapors. This process is often hard to observe, and highly kinetically dependent, so in situ techniques can be especially valuable to understand how to grow larger or better crystals, how to choose phases more precisely, and how to discover entirely new materials. With a clearer view of how materials form, we can critically evaluate computational predictions (ab initio or machine-learned methods) and explore novel reactions to target new phases.