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The growth and progression of most solid tumors depend on the initial transformation of the cancer cells and their response to stroma-associated signaling in the tumor microenvironment 1 . Previously, research on the tumor microenvironment has focused primarily on tumor-stromal interactions 1-2 . However, the tumor microenvironment also includes a variety of biophysical forces, whose effects remain poorly understood. These forces are biomechanical consequences of tumor growth that lead to changes in gene expression, cell division, differentiation and invasion 3 . Matrix density 4 , stiffness [5][6] , and structure 6-7 , interstitial fluid pressure 8 , and interstitial fluid flow 8 are all altered during cancer progression.Interstitial fluid flow in particular is higher in tumors compared to normal tissues [8][9][10] . The estimated interstitial fluid flow velocities were measured and found to be in the range of 0.1-3 μm s -1 , depending on tumor size and differentiation 9, 11 . This is due to elevated interstitial fluid pressure caused by tumor-induced angiogenesis and increased vascular permeability 12 . Interstitial fluid flow has been shown to increase invasion of cancer cells [13][14] The technique presented here imposes interstitial fluid flow on cells in vitro and quantifies its effects on invasion (Figure 1). This method has been published in multiple studies to measure the effects of fluid flow on stromal and cancer cell invasion [13][14][15]17 . By changing the matrix composition, cell type, and cell concentration, this method can be applied to other diseases and physiological systems to study the effects of interstitial flow on cellular processes such as invasion, differentiation, proliferation, and gene expression. Video LinkThe 3. Mix components of the gel on ice in the same sequence as above and incubate final solution for 1 hr at 4°C. In our experience, a 1 hr incubation prior to cell seeding results in a more uniform gelation of the collagen. Make sure to keep Matrigel and collagen on ice at all times and to work as fast as possible to prevent gelation.