Flow visualization techniques have evolved significantly over the past few decades, starting from qualitative 1D and 2D methods to quantitative 3D methods in recent years. A few different flow and thermal visualization techniques will be introduced that have been utilized for various fundamental to applied applications. Particle image velocimetry (PIV) was used to quantify the interaction of particles with a very fundamental type of turbulent flow: homogeneous and isotropic turbulence without mean flow. Magnetic resonance velocimetry (MRV) is a non-intrusive flow visualization technique, which is able to measure the 3 dimensional 3 component (3D3C) mean velocity field of complex flows using an MRI scanner. This method has been employed to characterize the 3D flow field from simple geometries such as fully developed turbulent pipe flow, to complex geometries such as gas turbine internal serpentine cooling passages. Planar laser induced fluorescence (LIF) was used to measure scalar distributions of fuel concentration and relative temperature in a homogeneous charge compression ignition (HCCI) internal combustion engine.