I made a puree of maraschino cherries and added 2.5g of calcium lactate gluconate. I then dripped this mixture into a solution of 2.5g of sodium alginate in 500g of water. A gelatinous skin is formed at the interface between the two liquids, forming spheres of cherry puree. This process is known as reverse spherification. I bought the chemicals here: http://www.amazon.com/Experimental-Kit-Artistre-600-grams/dp/B0045KOOXU