Microgravity induces changes in the cytoskeleton. This might have an impact on cells and organs of humans in space. Unfortunately， studies of cytoskeletal changes in microgravity reported so far are obligatorily based on the analysis of fixed cells exposed to microgravity during a parabolic flight campaign (PFC). This study focuses on the development of a compact fluorescence microscope (FLUMIAS) for fast live-cell imaging under real microgravity. It demonstrates the application of the instrument for on-board analysis of cytoskeletal changes in FTC-133 cancer cells expressing the Lifeact-GFP marker protein for the visualization of F-actin during the 24(th) DLR PFC and TEXUS 52 rocket mission. Although vibration is an inevitable part of parabolic flight maneuvers， we successfully for the first time report life-cell cytoskeleton imaging during microgravity， and gene expression analysis after the 31(st) parabola showing a clear up-regulation of cytoskeletal genes. Notably， during the rocket flight the FLUMIAS microscope reveals significant alterations of the cytoskeleton related to microgravity. Our findings clearly demonstrate the applicability of the FLUMIAS microscope for life-cell imaging during microgravity， rendering it an important technological advance in live-cell imaging when dissecting protein localization.