The present invention provides an O/W type emulsion having a volume median diameter of not more than 100 nm and containing a compound represented by the formula (1)wherein Xa and Xb are each independently X1, X2 or a 1,4-piperazinediyl group s is 1 or 2,R4 is an alkyl group having 1 - 6 carbon atoms,na and nb are each independently 0 or 1,R1a, R1b, R2a and R2b are each independently an alkylene group having 1 - 6 carbon atoms,Ya and Yb are each independently an ester bond, or the like, andR3a and R3b are each independently a liposoluble vitamin residue or the like.
