The main focus of this thematic collection is on the antimicrobial activity of essential oils and their combinations with conventional antimicrobial drugs, including the eradication of the existing biofilms, the explanation of the mechanisms underlying antimicrobial activity, and the preparation of stable formulations with essential oils, which boost their antimicrobial activity and provide greater stability. These issues are addressed in four research papers and three reviews, which present novel advances in the development and application of essential oils as antimicrobial agents via combinatorial and nano-based approaches.