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The mass function of galaxies and clusters of galaxies can be derivedobservationally based on different types of observations. In this study we testif these observations can be combined to a consistent picture which is also inaccord with structure formation theory. The galaxy data comprise the opticalgalaxy luminosity function and the gravitational lensing signature of thegalaxies, while the galaxy cluster mass function is derived from the X-rayluminosity distribution of the clusters. We show the results of the comparisonin the form of the mass density fraction that is contained in collapsed objectsrelative to the mean matter density in the Universe. The mass density fractionin groups and clusters of galaxies extrapolated to low masses agrees very wellwith that of the galaxies: both converge at the low mass limit to a massfraction of about 28\% if the outer radii of the objects are taken to be$r_{200}$. Most of the matter contained in collapsed objects is found in themass range $M_{200} \sim 10^{12} - 10^{14} h^{-1}_{70} M_\odot$, while a largeramount of the cosmic matter resides outside of objects with radius $r_{200}$.

Galaxies and Cluster of Galaxies as Peak Patches of the Density Field