Over the last two decades, miniaturization, integration, and automation have made microfluidic systems popular. Core to advances in microfluidics are numerous electrophoretic separation and preconcentration strategies, some finding their origins on bench-top systems. Among them, gradient-based strategies are especially effective in addressing sensitivity challenges. This review introduces several gradient-based techniques according to a broad definition, including conductivity, field, and concentration, organized by the method of gradient generation. Each technique is introduced and described, and recent seminal advances explored.