## 1 Introduction  
One of the promising directions in the development of industrial biotechnology is the production and application of microalgae biomass [1, 2]. Compared to other types of plant biomass, microalgae exhibit very high photosynthetic efficiency, fast growth rates, and resistance to various pollutants in their culture environment [3]. In addition, microalgae can be cultivated on land that is unsuitable for traditional agriculture or for investment purposes [4, 5]. The wide variety of microalgae strains available enables their use in various fields, including bioenergy production, food production, synthesis of omega-3 fatty acids, animal feed, organic fertilisers, biodegradable plastics, recombinant proteins, pigments, pharmaceuticals, and vaccines [6, 7]. Most scientific publications focus on the use of microalgae biomass for the production of biofuels such as biodiesel, bioethanol, biogas, biohydrorogen, and aviation fuels [8, 9, 10, 11, 12]. However, the realisation of efficient and economically viable technologies for the production of microalgae biomass and their application in the commercial sector remains a major challenge [13]. Current issues facing researchers, engineers and operators of microalgae-based energy systems include the development of efficient cultivation protocols, methods for concentrating and separating the biomass from the culture medium, dewatering and drying processes, and techniques for extracting valuable bioproducts [14]. A crucial aspect is the identification and selection of factors that influence the intensification of microalgal biomass growth and the increase in the yield of target substances, including the optimisation of the chemical and physical parameters of the cultivation environment [15]. Based on previous research, an important prerequisite for the further development of microalgae cultivation on an industrial scale is the development of solutions that are both economically and technologically feasible and at the same time ecologically sustainable [16]. A key factor in improving cultivation efficiency is the provision of optimal conditions in photobioreactors (PBRs) [17]. This goal can be achieved primarily through the development and implementation of advanced systems for monitoring, control, and automation of microalgae culture processes [18]. For industrial-scale systems, especially for large-scale operations, the use of online monitoring is recommended. This enables real-time process monitoring and allows a rapid response to fluctuations, directly improving cultivation performance [19]. Such monitoring also contributes to greater efficiency in the removal of contaminants and the production of high-quality end products. The implementation of effective monitoring and control systems requires the integration of reliable sensors capable of continuously measuring the environmental conditions, the physico-chemical parameters of the culture medium and the biological variables related to the processes within the PBRs [20]. The current focus is on the development of intelligent systems based on Internet of Things (IoT) technologies, artificial intelligence (AI) algorithms, and process automation using advanced sensors and predictive algorithms. There is also a growing interest in smart PBRs that are able to regulate culture conditions in real time. The dynamic development of these technologies and the lack of comprehensive studies integrating the latest monitoring solutions justify the need for this overview. The aim of this study is to present the current state of knowledge, scope, approaches, and methods for system monitoring of intensive production of microalgae and the detection of target and valuable end products that accumulate in the biomass. In the following chapters, a bibiological analysis of the analysed topic, the application directions and economic use of microalgae are presented, and the parameters of the microalgae cultivation process and the environmental conditions that require close monitoring are described, as well as the tools used.