A method of examining chicken eggs during an incubation period in an incubation system, comprising a housing for accommodating chicken eggs using at least one tray supporting said eggs, and a heater for heating an interior of said housing, the method comprising: measuring radiation response from each of the eggs to illumination of a predetermined spectral range during different time intervals of the incubation period to identify the presence of an alive embryo in said egg based on measured data indicative of said measured radiation response, and wherein the method is characterized in that said measuring of the radiation response from each of the eggs comprises providing, in said incubation system, a monitoring system comprising: an optical unit integrated to be part of said at least one incubation tray, the optical unit being positioned inside the housing in at least one of the following configurations: above the tray, below the tray, or inside said tray, and being configured and operable for continuously or periodically providing measured data indicative of the radiation response from the egg during the different time intervals of the incubation period; and a control unit configured and operable for analyzing the measured data and identifying presence of the alive embryo in said egg, wherein said analyzing comprises identifying predetermined dynamics in variation of intensity of said radiation response from said egg during the different time intervals of the incubation period and monitoring a development stage and age of the embryo being developed in said egg based on the identified predetermined dynamics in the intensity variations, said predetermined dynamics in the intensity variations of the radiation response during the different time intervals of the incubation period comprising at least one of the following: a change in a frequency of variation of the intensity of the radiation response at the different time intervals, appearance and disappearance of a certain frequency of variation of the intensity of the radiation response, a change in an amplitude of the intensity varying at a certain frequency. measuring radiation response from each of the eggs to illumination of a predetermined spectral range during different time intervals of the incubation period to identify the presence of an alive embryo in said egg based on measured data indicative of said measured radiation response, and wherein the method is characterized in that said measuring of the radiation response from each of the eggs comprises providing, in said incubation system, a monitoring system comprising: an optical unit integrated to be part of said at least one incubation tray, the optical unit being positioned inside the housing in at least one of the following configurations: above the tray, below the tray, or inside said tray, and being configured and operable for continuously or periodically providing measured data indicative of the radiation response from the egg during the different time intervals of the incubation period; and a control unit configured and operable for analyzing the measured data and identifying presence of the alive embryo in said egg, wherein said analyzing comprises identifying predetermined dynamics in variation of intensity of said radiation response from said egg during the different time intervals of the incubation period and monitoring a development stage and age of the embryo being developed in said egg based on the identified predetermined dynamics in the intensity variations, said predetermined dynamics in the intensity variations of the radiation response during the different time intervals of the incubation period comprising at least one of the following: a change in a frequency of variation of the intensity of the radiation response at the different time intervals, appearance and disappearance of a certain frequency of variation of the intensity of the radiation response, a change in an amplitude of the intensity varying at a certain frequency.