Combustion engines for automotive, locomotive, land, ships, and aircraft utilize liquid fuel injected into combustion chambers. Projected increases in the price of fuel and the effects of emissions on pollution and climate change are requiring increased efforts to increase combustion and energy efficiency within combustion chambers together with minimizing emission of particulates, including oxides of nitrogen and sulfur and other pollutants, including CO2. The question that is being addressed is how research can contribute to the objective of improving the efficiency of engines using liquid fuel and reducing the amount of pollutants generated in the energy conversion process by control of drop size, velocity, and trajectory and local air/fuel mixture ratios which have a dominant influence on ignition, combustion, and exhaust emissions. Basic predictions of global spray combustion phenomena may not result in sufficient understanding that can lead to the necessary improvements. Advancing our knowledge of the associated phenomena with careful experimentation and modeling can hold the key to a deeper understanding of the involved processes and thus can result in the required improvements. This paper provides a brief overview of the current state and challenges in some of the key research areas related to understanding the processes involved in liquid fuel combustion. It represents a summary of a Forum discussion titled "Spray Control for Maximizing Energy Efficiency and Reducing Emission in Combustion Engines" held at the ILASS-Americas 22nd Annual Conference on Liquid Atomization and Spray Systems in Cincinnati, Ohio.