It doesn't get much cooler in the robotic-arm-kit game. The assembled STEM educational arm is 15" tall x 9" long x approx 3-1/2" wide. It's 2-pronged hand opens to 1-3/4", lifts up to 3.5 oz (100g), swings 120 degrees at the wrist, pivots 300 degrees at the elbow, and sits on a base that swings 180 degrees up and down and rotates 270 degrees, like, well, an arm. Controlled by (5) 2-axis joy-sticks and powered by (4) D-Cell batteries that you provide. Includes a hand-mounted search light and over-torque and gear-breakage alarms, which is more than your arm has. Requires a diagonal cutter and Philips screwdriver for assembly of its 200+ pieces and is made for ages 12 and up.

Start your children on the path to learning the basic concepts of solar tech. This multi-bot STEM education solar kit includes a 1.5V solar cell, a small DC motor and gearbox and a boatload of parts that will let you make (14) different comical and functional land and water solar-powered projects including: TortoiseBOT; SlinkerBOT; FourBOT; SurferBOT; PaddleBOT; WalkR-BOT; Big Wheeler BOT; CarBOT; TumblerBOT; BugBOT; K9BOT; MonsterBOT; CrabbyBOT and, you should pardon the pun, the RowingBOT. No, really--there's a row bot. Projects come in (2) levels of difficulty and include an 81pp graphic manual. You'll need a hobby knife or a pair of side-cutters, and sunlight. Most projects will be approx 5" tall when assembled.

Lego® goes crazy with this 100+ piece kit with everything you need to build (16) different contraptions (be pretty stupid if they made 16 of the same contraption) for your amusement. In the mix are gears, pulleys, belts and axles, which you could turn into a rocket racer, Lego® launcher, donkey cart or scissor grabber, among other things. Includes a 50-page spiral-bound graphically illustrated instruction booklet. And, yes, adding Lego® pieces of your own just ramps up the fun. For ages 7+.

We woodn't kid you; we always like wooden kits best. More organic. These are all pre-cut, unfinished pine and include nails. You add wood glue, simple hand tools and paint. This little birdhouse, which will be approx 6" long x 3-1/4" square will keep your small feather friends happy and protected from the elements. Great as a craft project by itself, or a handy science teaching aid for youngsters or young adults that are ready to be kicked out of your nest. Ages 8+.

This Lego® set from Klutz has (58) pieces, including gear wheels, bricks, axles and connectors to build (11) gadgets, including a claw, catapult, assorted vehicles, robots, a fan and a hand-held blender thingy. Includes a 78-page manual with detailed instructions and a plethora of punch-out paper parts for added verisimilitude. For ages 8+, or anyone else who knows what plethora and verisimilitude mean.

From Elenco®, than whom nobody is cleverer, this MECH5 kit--a STEM kit--will make (5) robots, all of which use a mechanical coding wheel instead of software. They perform tasks, including forward, back 45 or 90 degrees, left or right turns, and modes to make bots draw circles, throw or push a ball, grip things, or act as a forklift. You add (2) “AAA” batteries for the small DC motor. Kit has (220+) pieces and the finished bots will be approx 6” tall. Ages 10+, but it’s intricate enough to need some adult help unless the kid is a genuine whiz-bang.

Make a whole bunch of fun and instructive Lego® machines/chain reaction models like marble runs and mousetraps involving ramps, buckets, funnels balances and much more. Comes with (33) Lego® elements, (6) Lego® balls, a dozen paper props, and a 78-page instruction booklet for (10) machines. You add a few common household items. Includes suggestions for more complicated devices if you have your own Lego® pieces, and if you don't, what are you waiting for? Ages 8+.

Right after you build your own working medieval catapult or trebuchet. All you’ll need is glue, scissors and a steady hand (plus a small bag of marbles or rocks or something as a counterweight for the trebuchet) to construct these wooden, Canadian-made siege engine kits. The catapult stands 6” tall x 5” wide x 10” long and will toss assorted stuff 15 feet or farther, depending upon the stuff. The finished trebuchet will be 26” long x 18” wide x 24” tall and will propel small objects (meatballs?) 20 feet or more. Both include detailed instructions and are great resources for STEM activities. For ages 9+. Note: Please don’t propel small mammals, and please don’t put anyone’s eye out.

Among other things. (Sorry, no oranges.) Our each is a set of (4) laser-cut moving wooden gear models from U-Gears®, including a cat, a tractor, a human head and a heart. You like to fidget? Us, too. Each has (6) or (7) laser-cut parts and will fit in the palm of your hand when finished. They’re like worry beads in that you'll find yourself playing with them to help you inch toward inner peace. They’re press-fit, so no glue or tools needed. For ages 5 and up.

Nice little pulley unit kit includes (1) pulley each at 50, 30, 25 and 20mm and (3) pulleys at 11mm, plus myriad bushings, a 3VDC motor, (2) belts and a belt guide, base, mounts and assorted hardware. Includes graphic assembly instructions, plus a couple of rudimentary drawings with suggested projects. It's a mechanical science project waiting for a home.