One embodiment of the invention relates to a microfluidic apparatus for performing two dimensional biomolecular separations. According to one aspect of the invention, after a first dimension separation in a first microchannel, the sample material is electrokinetically and simultaneously transferred to an array of microchannels in the second dimension (e.g., by changing the electric potentials at the reservoirs connected to the microchannels). Preferably any separation accomplished in the first dimension is completely retained upon transfer to the second dimension. According to another aspect of the invention, the separation in the second dimension is performed using a temperature gradient (e.g., a spatial or temporal temperature gradient). According to one embodiment of the invention, the biomolecular material comprises DNA and the first dimension separation is a sized-based separation and the second dimension separation is a sequence-based separation.