genetic materials, and imaging agents are also required to be delivered to a target location in the biomedical field for medical diagnostics and treatments [9; 10]. Nanomedicine [11] and microrobotics are two approaches that can be utilized for targeted drug delivery. Therefore, microrobotics is an important field of study in microfluidics research. A microrobot is an intelligent, reprogrammable, microscale robotic system fabricated using microfabrication techniques to move, sense, and operate inside a microenvironment [12]. Most commonly, microrobots used in medical applications are operated inside a fluidic environment in the microscale [13]. Therefore, the microrobots discussed in this review are related to the microfluidic domain. Various classifications of microrobots are reported based on their make-up, operating region, actuator placement, and propulsion method [12]. According to the make-up, microrobots are classified as cellular microrobots, synthetic microrobots, and hybrid microrobots [14]. Cellular microrobots are based on cell-made components and synthetic microrobots are made of man-made components [15]. Hybrid microrobots contain both cell made components and man-made components [16]. Microrobots are divided into two groups such as microswimmers and surface walking robots according to the operating region. Microswimmers [17] can propel and move inside a bulk fluid. Conversely, surface walking robots can walk [18], slip [19], or roll [20] on the fluidic walls. According to the actuator placement, microrobots are categorized as on-board and off-board robots [21]. On-board microrobots have the capability to move, sense, and operate independently without any external interaction whereas off-board microrobots require external interference [12]. In classification according to the propulsion method, the actuation technique is significant. Microobots are actuated using magnetic [22], acoustic [19], optical [23], chemical [24], and mechanical [25] actuation methods. From the mentioned actuation methods, magnetic actuation is a widely used actuation method, which is used to mobilize microrobots in biomedical applications [26]. In magnetic actuation, the use of external magnetic fields is considered the most successful approach [3]. This is because low-frequency and low-strength magnetic fields are not harmful to biological matters including the vital organs in the human body [27], providing the magnetic environment near the microrobot can be achieved using a permanent magnet or an electromagnet. However, the magnetic field strength decreases at a greater rate with the distance from the source [28]. This is a challenge in designing and choosing the magnetic propulsion method. However, this approach is suitable for both in vitro and in vivo applications [29]. The major challenge in exploring the fluid and particle behavior in the microenvironment is that the fundamental theories differ from that of the macroscale [30; 31]. For example, viscous forces dominate the inertial forces in the microscale [32]. This happens in the low Reynold's number fluid regime of Newtonian fluids. Reynold's number can be calculated using the density of the fluid, length of the microrobot, swimming speed of the microrobot, and the dynamic viscosity of the fluid [33]. For microrobots, length and swimming speed are in microscale. Therefore, the flow regime of a microrobot always has a low Reynold's number. According to the scallop theorem, microrobots that do not have a non-reciprocal motion cannot propel in Newtonian fluids [34]. Mimicry of natural matter is a promising approach in addressing this challenge and various bio-inspired systems have been investigated [35]. Bio-inspired mechanisms have been implemented for microrobots and various propulsion methods have been investigated [36]. In this review, biological systems which are capable of generating non-reciprocal motion are focused on. Specifically, the motion of bacteria flagella, sperm flagella, cilia, and fish have given inspiration in propelling microrobots [35].