A modular microfluidic system comprising a base substrate, a plurality of microfluidic assembly blocks, and an adhesive component is provided. Each individual microfluidic assembly block defines a channel and has a sidewall defining an aperture into the channel. When the plurality of microfluidic assembly blocks are arranged on the base substrate, the aperture into the channel of one microfluidic assembly block aligns with the aperture of another microfluidic assembly block with the channels thereof connected along a plane parallel to the base substrate thereby forming a channel network defined by the plurality of microfluidic assembly blocks. The subject invention also provides a method of assembling a microfluidic device. The method comprising the steps of providing the base substrate, providing the plurality of microfluidic assembly blocks, and arranging the plurality of microfluidic assembly blocks on the base substrate.