###### Abstract
The oceans play a vital role in Earth's climate due to their capacity to redistribute heat across the globe and to absorb and store greenhouse gases, primary productivity of the oceans accounts for 48.5 Pentagrams of carbon per year (0.65 Pg C y\({}^{-1}\)), which corresponds to almost half of total Earth primary production [3]. In particular, the mixed layer of the oceans has an effective heat capacity 20 times that of the effective heat capacity of the entire atmosphere [4; 5]. The oceans have taken up more than 90% of the excess heat in the climate system that results from the anthropogenic greenhouse gases (GdG) emissions [6], making them a critical regulator of our climate's thermal balance. They also play a vital role in the thermal memory of the climate system since deep currents govern climate change in a millenia timescale and the surface currents do the same in the short term (years) [7]. Satellites have been crucial in estimating not only primary production at sea [8] but also on deriving EO data on oceanic heat content [9; 10; 11; 12]. However, as we will see, the resolutions used are not sufficient to study smaller regions that must be incorporated in environmental variables. Lakes, although not matching the oceans in heat storage capacity, are vital in terms of primary production, with a substantial global impact. Global gross primary production (GPP) in lakes is estimated to be 0.65 Pg C y\({}^{-1}\)[13]. The rate of organic carbon burial in inland water sediments exceeds that of organic carbon sequestration on the ocean floor [14]. Additionally, lakes serve as sensitive indicators of climate change through shifts in phytoplankton phenology, ice melting patterns, and temperature variations [15]. They also play a significant role in regulating greenhouse gases, and the shrinking of lakes--combined with surface runoff, atmospheric deposition, and biogeochemical transformation--amplifies greenhouse gas re-emission, particularly in smaller (less than 1 km\({}^{2}\)) lakes [16]. There are more than 117 million lakes in the world [17]. Moreover, very small ponds, of less than 0.001 km\({}^{2}\), comprise 8.6% of lakes and ponds by area globally, but account for 15.1% of CO\({}_{2}\) emissions and 40.6% of diffusive CH\({}_{4}\) emissions [18]. Furthermore, lakes influence regional climate, acting as local coolants [19] and by dampening the variability in near-surface temperature such as in the Great Lakes area, affecting the living of millions of people [20]. Finally, saline lakes contribute two times more to the emission of CO\({}_{2}\) than freshwater lakes [21]. The importance of satellites for the monitoring of lakes has been stated by previous research [2]; however, we review the bottlenecks on the use of EO for lake monitoring and assess if monitoring of lakes health and water quality parameters is already possible on a global scale so as to include lake colour as an essential climate parameter. Despite their importance, most lakes are small and shallow. It is [22] estimated that 304 million lakes exist globally, of which 91% are of the smallest size (0.001-0.01 km\({}^{2}\)), and the average lake is 0.012 km\({}^{2}\)[22]. Most lakes, therefore, are typically shallow with plenty of light and nutrients but they emit similar amounts of carbon to the atmosphere as the global terrestrial net ecosystem production [14]. Studying very small lakes or water bodies over extensive areas and different habitats can be of great value to better understand climate change. For further reference, we define \"very small lakes\" in this paper as less than 0.4 km\({}^{2}\); such a value is important since the resolution of Sentinel-3 is 300 m, which is not suitable to study water bodies less than 600 m in extension or 0.36 km\({}^{2}\). The resolution of Sentinel-2 is 20 m (HR2) and of Landsat-8 is 40 m (MR1).