NOVELTY - Making fatty acid lower alkyl esters by transesterification of fatty acid glycerides with lower aliphatic alcohols where the reaction takes place in a micro-mixer connected to a capillary, involves: (a) heating fatty acid glycerides (compound a) to a temperature of 45-65 degrees C; (b) preheating a mixture of lower aliphatic alcohol and an alkaline catalyst (compound b) to a temperature of 20 to 50 degrees C; (c) feeding both compounds (a) and (b) into micro-mixer for transesterification; and (d) obtaining the reaction mixture and leaving the micro-mixer is fed into capillary or tube for residence.    USE - The process is useful for making fatty acid lower alkyl esters by transesterification of fatty acid glycerides with lower aliphatic alcohols. The fatty acid lower alkyl esters are useful as biodiesels (all claimed).    ADVANTAGE - Improved transesterification is provided using micro-mixer systems with respect to time of reaction and selectivity. In conducting transesterification in micro-mixer under liquid/liquid conditions, more particularly at temperatures of at least 65 degrees C and pressures of at least 1.1 bar, a higher mixing intensity and a faster reaction can be achieved.    DETAILED DESCRIPTION - Making fatty acid lower alkyl esters by transesterification of fatty acid glycerides with lower aliphatic alcohols where the reaction takes place in a micro-mixer connected to a capillary, involves: (a) heating fatty acid glycerides (compound a) to a temperature of 45-65 degrees C; (b) preheating a mixture of lower aliphatic alcohol and an alkaline catalyst (compound b) to a temperature of 20 to 50 degrees C; (c) feeding both compounds (a) and (b) into micro-mixer for transesterification, where the mixture is heated under a pressure of about 1.1 to about 3 bar to a temperature of about 65 to about 100 degrees C; (d) obtaining the reaction mixture and leaving the micro-mixer is fed into capillary or tube for residence; and optionally (e) subjecting the reaction product to a separation step for purification.