Dark Matter and Gravitational Lensing
  The last decade has shown a considerable development of gravitational lensing for cosmology because it probes the amount and the nature of dark matter, and provides information on the density parameter $\Omega$, the cosmological constant $\Lambda$ and the Hubble constant $H_{o}$. Therefore, gravitational lensing can constrain the cosmological scenario which gave birth to the Universe as it appears today. The ongoing programs and future projects which are developing now all over the world show that gravitational lensing is considered as a major cosmological tool for the coming years as well. In this review, we summarize some of the most recent advances in the fields relevant for the dark matter issue. We will focus on the microlensing, the arc(let)s and the weak lensing studies. The possibility to check the existence of a non-zero $\Lambda$ is presented elsewhere. 
Y. Mellier (1,2), F. Bernardeau (3), L. van Waerbeke (4) ((1) IAP; (2)   Obs. Paris DEMIRM; (3) SPhT CE Saclay; (4) MPA Garc...